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GB 23 

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Copy 1 


Review Questions 

and 

Picture Studies 

in 

Physiography 


BY 

Albert L. Arey 

Girls’ High School (Retired) 

Frank L. Bryant 

Erasmus Hall High School (Retired) 

William W. Clendenin 

Wadleigh High School 


in New York City 



D. C. HEATH AND COMPANY 

BOSTON NEW YORK CHICAGO 

ATLANTA SAN FRANCISCO DALLAS 

LONDON 




































. 






/ 




» 























Review Qu estions 


and 


Picture Studies 


in 


Ph ysiography 



Albert L. Arey 

Girls’ High School ’(Retired) 

Frank L. Bryant 

Erasmus Hall High School (Retired) 

William W. Clendenin 

Wadleigh High School 
in New York City 



D. C. HEATH AND COMPANY 


BOSTON 

ATLANTA 


NEW YORK 
SAN FRANCISCO 
LONDON 


CHICAGO 

DALLAS 





Copyright, 1928, 

By D. C. Heath and Company 

2 h 8 



PRINTED IN U.S.A. 


SEP 17 1928 @cu 1054326 


FOREWORD 


Several teachers using our Physiography have asked that, when 
our New Physiography was published, it be accompanied by a booklet 
containing the review questions that we have used in our classes, 
and that our methods of applying the principles of visual instruction 
to the study of the illustrations in the book be explained therein. 

In complying with this request, we have made no effort to include 
questions on every illustration in the book that will repay the teacher 
for the time spent; we merely present several ways of beginning a 
discussion by the pupils of the lesson that the given illustration is 
expected to teach. 

If the discussion is slow in starting, it may be necessary for the 
teacher to state some interesting fact bearing on the subject of the 
illustration, but we believe that it is not best for the teacher to do 
much talking during the discussion by the pupils. It usually pays 
better to talk only so much as is necessary to answer direct questions, 
and to guide the pupils to the points to be brought out, without 
permitting them to wander too far afield. 

The best method is the one that arouses the most interest and leads 
to the most general discussion of the topic and to the comparison of 
related illustrations. 

In our own classes this method has resulted in greater uniformity 
in the scholarship of the classes and has covered the ground with 
much less effort on the part of the teacher. 

The following general guide to class discussion of textbook illustra¬ 
tions of physiographic features may be helpful. 

With the textbook open to the illustration to be discussed, or with 
an enlargement of the illustration placed where every one in the class 
can see it, we start the discussion by calling upon a pupil to answer 
the first question below, following it with the others in about the 
order given: 

1. What physiographic features are most prominent in this 
picture? 

2. Mention the conditions or processes that formed the fea¬ 
tures named. 

iii 


IV 


FOREWORD 


3. What physiographic agents have been active in the past, 
or are now active in forming the prominent features here 
shown ? 

4. If more than one agent may have been active, state which 
was probably more important. 

5. Name any minor feature noticed. State necessary con¬ 
ditions and processes concerned in bringing about each par¬ 
ticular feature named. 

6. Point out the relation between the tearing-down processes 
and the building-up processes in the region illustrated. 

7. What human interests do you think are influenced by the 
changes shown in the picture ? 

8. Has any pupil a question that will lead to a better under¬ 
standing of the activity illustrated? 

We do not require notes to be taken by the pupils but do not 
forbid them to take brief notes if they feel that they will not remem¬ 
ber what they have learned. 

Experience has taught us that this method will start discussion by 
the pupils in which they will be interested and from which they often 
obtain much information; furthermore the teacher will get the 'pupils’ 
point of view. 

May, 1928 


The Authors 


TABLE OF CONTENTS 


PAGE 

FOREWORD.iii 

REVIEW QUESTIONS.1 

PICTURE STUDIES.50 


v 


























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t 































REVIEW QUESTIONS 


CHAPTER I 

THE EARTH IN SPACE 

1. What is the cause of the apparent passage of the sun through 
the sky each day? 

2. What makes the sun appear to move from the east to the west? 

3. How many degrees does the sun appear to move each hour? 
How long does it take the sun to appear to move one degree ? 

4. How many miles does the earth at the equator actually rotate 
each day? How many miles each hour? 

5. What are three of the best evidences that the earth’s surface 
is curved? 

6. When-are the lengths of day and night equal at all places on 
the earth? 

7. How much does the longest day in summer differ from the 
shortest day in winter in the locality where you live? 

8. At places farther north is this difference in the length of days 
greater or less? 

9. Where, when, and why are the lengths of day and night 
unequal ? 

10. How long does it take the earth to go round the sun? What 
is this motion called? What is the path that it follows called? 

11. About how many miles a day does the earth travel in its orbit? 

12. What would be the length of our day and night if the period 
of rotation were equal to a period of revolution? 

' 13. What is considered the principal cause of our change of season? 
Why is the change regular? 

14. What effect upon the change of seasons would a greater inclina¬ 
tion of the earth’s axis have? A less inclination? No inclination 
from a perpendicular to the plane of the earth’s orbit? 

15. What determines the length of our seasons? 

16. What is meant by the solstices and equinoxes? Give the dates 
of occurrence. 

17. On what dates does the sun rise due east and set due west of 
an observer? Between what dates does it rise north of east and set 

1 


2 REVIEW QUESTIONS 

north of west? Between what dates does it rise south of east and 
set south of west? 

18. Where on the earth are the sun’s rays vertical at the dates 
given for solstices and equinoxes? 

19. Does the sun’s daily path through the sky shift north or south 
from December 21 to June 21? During this six-months period what 
change in the length of days is taking place in the northern 
hemisphere ? 

20. What determines the position of the tropic and the polar 
circles ? 

21. What is meant by the expression “ Land of the Midnight 
Sun”? Where is it? 

22. Where on the earth does the sun rise once a year and set once 
a year? Give the dates. 

23. How long at this location does the sun stay above the horizon? 
How would an observer be able to tell when he had reached this 
point ? 

24. Why is the sun not always the same distance from us? 

25. With the aid of a protractor it is possible to make an estimate 
of the time of exposure of the photographic plate from which Figure 
8 of the textbook was made. Explain how this might be done. 


CHAPTER II 

LATITUDE, LONGITUDE, AND TIME 

1. Define latitude, and explain why the length of the latitude 
degree is not the same everywhere. 

2. Give the approximate length of the latitude degree at the 
equator, and tell where the latitude degree is shortest and where 
longest. By how many miles does it vary? 

3. Define longitude and degree of longitude at any place; and 
explain why the length of the longitude degree varies. 

4. Give the approximate length of the longitude degree at the 
equator. By how many miles does it vary on the earth? 

5. Explain the analogy between locating a house in the city by 
the streets and avenues and locating a ship at sea by latitude and 
longitude. 

6. Define perpendicular, vertical, horizontal, zenith, horizon, alti¬ 
tude of a heavenly body, declination of the sun. 


REVIEW QUESTIONS 3 

7. How does a ship’s officer find the latitude of his ship by day? 
By night? 

8. In order to locate the ship, longitude must be found at the 
same moment. How is this done? 

9. Suppose the sky is cloudy or the ship is in a fog. How then 
is a ship at sea located? 

10. (a) How could you lay out a true north-south line by means of 
the sun? (6) How by the North Star? (c) How could you get the 
noon altitude of the sun? ( d ) How is the altitude of Polaris deter¬ 
mined ? 

11. Why is it that the shortest shadows do not always fall when 
watches and clocks read noon? # 

12. Correct time is determined by astronomical observatories on 
clear nights. Why is this necessary? 

13. Time service is now given the public by radio at different 
times of the day and by telegraph, usually at noon. How is this 
correct time obtained? 

14. Why is it that the sun is not a good timekeeper ? 

15. Explain the meaning of a.m., p.m., and m. 

16. Where on the earth do the days of the week first start, and in 
what direction do they travel? 

17. (a) When it is 9 a.m., May 1, at New York, 75° west longitude, 
what is the day and hour at 165° west? (6) At 120° east? (c) Ex¬ 
plain why it is necessary to omit a day in crossing the 180th meridian 
going west, and to repeat the date in crossing it going eastward. 

18. (a) Those who live on the time meridians have the same local 
time and clock time. ( b ) If you live on the seventy-fourth degree 
meridian west, what would be your local time and your clock time 
when it is noon in Chicago ? 

19. When it is noon in New York City, what is the time in San 
Francisco? In London? 

20. When Colonel Lindbergh flew across the Atlantic Ocean from 
New York to Paris, was the night for him longer or shorter than at 
either of these cities? Explain. 

21. What is the International Date Line, and what adjustments of 
time are made in crossing it? 

22. What is meant by leap year, and why is it necessary? 

23. What is the name of the calendar we now use, and what are 
its advantages over the Julian? 

24. How should you arrange a calendar with all the months the 
same length? 

25. How do the paths of sun, moon, and stars, because of the 


4 


REVIEW QUESTIONS 


rotation of the earth, stand with reference to the horizon of: (a) 
An observer at the equator? (6) An .observer at the poles? (c) An 
observer in any other latitude? 

26. (a) How is the “ daylight circle,” the line separating the 
lighted from the unlighted hemisphere, situated with reference to the 
rays of the sun? (6) How does the daylight circle divide the equa¬ 
tor? (c) How does it divide the parallels in the summer hemisphere; 
in the winter hemisphere? ( d ) When, if ever, does the daylight 
circle bisect all parallels? (e) Express this division of equator and 
parallels in terms of length of day and night. 

27. Determining longitude is always a comparison of times, one of 
which is of a place of known longitude, usually of Greenwich or zero 
longitude. The time of the prime meridian is carried on the chronom¬ 
eter of the ship, and local noon is determined. If the chronometer 
is jf aster than local time, the longitude of the place is west; and if the 
chronometer is slower, the longitude of the place is east. Example. 
Noon by the ship and 4 a.m. by chronometer: the ship is 8 hours or 
120° east of the prime meridian, or in 120° east longitude. Find the 
longitude of a ship whose chronometer shows 4 p.m. when it is noon 
by the ship. 

28. Define solar day, lunar day, and sidereal day. Explain why 
the sidereal day is measured by rotation of the earth through 360°, 
the solar day by rotation through about 361°, and the lunar day by 
rotation through about 373°. 

29. The earth is moving fastest in its orbit at perihelion. Why? 
Therefore the solar day is longest at that time and shortest at 
aphelion. No two consecutive solar days are of equal length; there¬ 
fore our clocks keep mean or average solar time. Will the sun come 
to the meridian before or after 12 by the clock in midwinter? In 
midsummer ? 

30. (a) Why do twilight and dawn last for a shorter time at the 
equator than in New Orleans? ( b ) Why longer in London than in 
St. Louis? (c) Make a general statement regarding the length 
of twilight and dawn in their relation to the latitude of a given 
location. 

31. (a) Why do the stars rise about four minutes earlier each 
night than the night before? (6) A star that rises at 6 a.m. will rise 
about what hour three months later? In what part of the sky will 
it then be seen at 6 a.m.? 

32. Explain the location of a ship by “ dead reckoning.” Explain 
its location by radio. 


CHAPTER III 

THE MOON 

1. Compare the moon and earth as to: (a) Size, (6) motions, 
(c) source of light, {d) suitability for life. ( e ) How much of the 
moon is always illuminated? 

2. How fast, measured in degrees, is the moon moving in its orbit 
about the earth ? In what direction is it moving ? 

3. Compare the mountains and valleys of the moon with those 
on the earth. 

4. Compare the length of day and night on the moon with the 
length of day and night on earth. To what is the difference due? 

5. (a) Why does the distance of the moon from the earth vary? 

( b ) What is the approximate distance of the moon from the earth? 

(c) Give the names for the points in the moon’s orbit nearest to and 
farthest from the earth. 

6. Why does the moon change phase, and how long does it require 
for the moon to go through its cycle of phases? 

7. How often do we have full moon? Explain. 

8. What is an eclipse? 

9. Compare the duration of an eclipse of the sun with that of the 
moon. Explain the difference. 

10. Astronomers often travel thousands of miles to study a total 
solar eclipse. Why is it considered so important? 

11. What is meant by lunar day , and why is it longer than a solar 
day? About how much longer is it? 

12. The period required for the moon to go through its cycle of 
phases is the lunar month, analogous to the earth year, (a) Why 
is this period longer than the time required for a complete revo¬ 
lution of the moon? ( b ) Give the number of days for each. 

13. ( a ) About how long after new moon is the moon in first-quarter 
phase? (h) Where do we see the first-quarter moon when the sun 
is setting? 

14. (a) How do you distinguish between the young crescent and 
the old crescent moon? (6) How between the first-quarter and the 
third-quarter moon? 

15. (a) In what part of the day or night do we see the first- and 

5 


6 


REVIEW QUESTIONS 


third-quarter moon? (6) At what phase of the moon is it of greatest 
value as a source of light? (c) Why? 

16. Between what phases of the moon is it waxing and waning? 
How can you tell a waxing from a waning moon ? 

17. (a) About what time of day does the full moon rise? ( b ) 
Where do we see the full moon at midnight? 

18. (a) Why do we never see the new crescent moon in the east nor 
the .old crescent moon in the west? (6) Why are we able to see the 
entire outline of the moon at new crescent and old crescent phases? 

19. (a) How do we know the moon rotates? ( b ) Give the period 
of rotation. 

20. (a) What is a shadow? (h) Why do the earth and moon cast 
shadows? (c) What is the position of these shadows with reference 
to the sun? ( d ) Why are these shadows cone-shaped? 

21. (a) Do we ever get into the earth’s shadow? ( b ) If so what do 
we call this phenomenon? (c) What do we call the phenomenon of 
being in the moon’s shadow? (d) At what phase of the moon do we 
get into its shadow? 

22. (a) Explain lunar eclipses. (6) Why does a lunar eclipse 
occur only at full moon? (c) Why is there not a lunar eclipse every 
full moon? 

23. There are more solar eclipses than lunar; yet you will not see 
so many solar as lunar. Why is this? 

24. If the umbra of the moon’s shadow reaches the earth, there 
will be a total eclipse of the sun; but if it does not reach the earth, 
there is an annular eclipse. Why should the shadow sometimes 
reach the earth and sometimes not ? 


CHAPTER IV 
THE SOLAR SYSTEM 

1. (a) Name the classes of heavenly bodies that you can see with 
the naked eye. ( b ) How do you recognize each class? (c) Which 
of these classes belong to the solar system ? 

2. Planets are often called stars. How do planets and stars 
differ? 

3. Name the (a) smallest planet, ( b ) the largest, (c) the planet 
that comes nearest the earth, (d) the planet most like the earth, and 
(e) the planet with the longest year. 


REVIEW QUESTION^ 7 

4. (a) What planets may pass between the earth and the sun? 
(6) Which planets are larger than the earth? 

5. (a) Name the planets in the order of their size; ( b ) in the 
order of their distance from the sun. 

6. (a) What is the length of the day on Jupiter? ( b ) Jupiter’s 
axis of rotation is nearly perpendicular to its orbit. What effect 
should this have on its seasons? 

7. (a) What are planetoids? (6) How many are there? (c) 
W'here are they located? 

8. (a) What light makes it possible to photograph the planetoids? 
(6) State two reasons why they are never seen with the naked 
eye. 

9. Compare the diameter of the sun with the diameter of the 
orbit of the moon. 

10. (a) How do we know that the sun rotates? (b) Compare its 
period of rotation with that of the earth. 

11. (a) What are sun spots? (6) What apparent effect do sun 
spots have upon the earth? 

12. Account for the light of the sun. 

13. What solar phenomena are seen only at the time of a total 
eclipse of the sun? 

14. How does our sun compare in size with the largest stars ? 

15. Why are certain comets considered members of the solar 
system ? 

16. Name two comets so considered and give their periods of 
revolution. 

17. In what respect are comets and stars alike, and in what respect 
are they different? 

18. (a) What is a satellite? (6) What satellites of other planets 
may be seen with an opera glass? 

19. Explain how the satellites of other planets may be eclipsed. 

20. How does the size of our moon compare with that of the 
satellites of other planets? 

21. (a) What are shooting starsf ( b ) By what name are they 
properly called? 

22. (a) What is a meteorite? (b) Of what are they usually com¬ 
posed ? 

23. What is the weight of the largest meteorite known? 

24. Certain stars are known to have bodies revolving about them. 
What does this suggest? 

25. (a) What is a nebula? (b) Describe a spiral nebula, (c) 
How large are the largest nebulae? 


8 ^REVIEW QUESTIONS 

26. What changes now taking place in nebulae suggest a theory of 
the origin of planets ? 

27. State the nebular hypothesis. 

28. According to the nebular hypothesis, which is older, Jupiter or 
Mars ? Saturn or its moons ? 

29. State the planetesimal hypothesis. 

30. According to the planetesimal hypothesis, how is the movement 
of the satellites about the planets explained? 

31. Contrast the nebular and the planetesimal hypotheses as to the 
origin of the sun, the moon, the ocean, the air. 

32. (a) How do meteors give us a measure of the depth of the 
air? (6) What makes them become visible? 


CHAPTER V 

MAP PROJECTION 

1. What is a map? 

2. (a) What does orthographic mean? (b) In what ways does 
an orthographic picture agree with this definition? (c) Describe 
the process of orthographic projection. 

3. For what kinds of maps is orthographic projection used? 

4. Construct an orthographic polar projection of the earth. 

5. (a) Describe the Mercator projection. (6) State its advan¬ 
tages and disadvantages, (c) To what part of such a map does the 
scale apply? (d) Why not to all parts? 

6. (a) Describe the Mollweide projection. (6) State its advan¬ 
tages and disadvantages. 

7. State the advantages of globes. 

8. (a) What is meant by'the scale of a globe? ( b ) To what 
part or parts does it apply? 

9. Mention several kinds of maps in which true scales can apply 
only to certain portions. 

10. What maps may have scales? 

11. (a) What are models? (b) State their advantages and dis¬ 
advantages. 

12. (a) How is relief best represented? (6) Describe a hachure 
map. 

13. (a) What is a contour line? (b) Mention several advantages 
of a contour map. 


REVIEW QUESTIONS 


14. Define contour interval. 

15. On the map of Grass Lake, Figure 37, locate two points, A and 
B, either of which could be seen from the other point. Also locate 
two points not in sight of each other. 


CHAPTER VI 

PROPERTIES AND FUNCTIONS OF THE AIR 

1. Give examples of man’s relation to his atmospheric environ¬ 
ment: (a) With respect to his food, ( b ) with respect to his clothes, 
(c) with respect to his housing. 

2. What is the basis of our estimate of more than two hundred 
miles as the height to which the atmosphere extends ?' 

3. What reason have we to think there is air enmeshed or dis¬ 
solved in the waters of the earth? 

4. What practical uses are made of the properties of compressibil¬ 
ity and elasticity of the air? 

5. What properties of the air make possible: (a) the windmill, 
( b ) the balloon, (c) the airplane, (d) the sailing vessel, and (e) the 
airship ? 

6. Why may the ordinary type of balloon not be directed in its 
course? 

7. What is meant by the statement that the air is a mechanical 
mixture f Would that mixture be called air if there were no water 
vapor nor dust in it? 

8. Why is there more dust in the air over the land than over 
the sea, and more water vapor in the air over the sea than over the 
land? 

9. Why are both dust and water vapor more abundant in the 
lower air than at higher altitudes ? 

10. (a) Why does a balloon rise? ( b ) Why does it sometimes 
float at a constant level? (c) How can it be made to descend? (d) 
How can it be made to rise higher? 

11. (a) Define diffusion. (b) What property of the air is due to 
diffusion ? 

12. (a) Why does carbon dioxide vary at any place, and why is it 
more abundant at some places than at others? (b) When and where 
is carbon dioxide most abundant? 

13. (a) What are the chief sources of the dust in the air? (6) 


10 


REVIEW QUESTIONS 


Distinguish between organic dust and inorganic dust, (c) Which 
kind do you consider the more objectionable, and why? 

14. How is the air naturally cleansed of its dust? 

15. Why does not the dust of the air accumulate on the underside 
of a table to the same extent as on top of the table? 

16. (a) Why is mountain air purer than the air at lower altitudes? 
( b ) Is this the only reason why sanitariums are so frequently located 
in mountains? 

17. Name all the functions of the air as a whole you can recall, 
arranging them in tabular form. 

18. (a) Name the various functions of oxygen. (6) Why is it 
necessary for aviators who rise high in the air to carry a supply of 
oxygen with them? 

19. (a) Name several substances with which iron is coated to 
prevent corrosion by the action of the air. ( b ) Why does not the 
“ stainless steel ” rust ? 

20. How does oxygen “ purify the air ”? 

21. Why is oxygen excluded from our electric-light bulbs? Note. 
The first bulbs were vacuum bulbs, but now they are filled with 
argon or nitrogen to give more stability to the incandescent filaments. 

22. (a) How do plants make use of the carbon dioxide in the air? 

( b ) Under what conditions do plants give out carbon dioxide? 

23. If there were more carbon dioxide in the air how would 
this affect our summers? Our winters? Note. It is thought there 
was a time when carbon dioxide was more abundant in the air 
than now and that this greater abundance was the cause of glacial 
climates. 

24. Give the round of processes by which carbon dioxide is re¬ 
moved from the air by plants and restored again to the air. 

25. Under what conditions will the carbon dioxide be, in part only, 
restored to the air, the remaining part in the form of carbon being 
accumulated in the form of coal? 

26. (a) Trace the processes by which plants get and use the nitro¬ 
gen of the air. (5) Enumerate the common “ nitrogen gatherers.” 

(c) Is the nitrogen thus gathered usable by other plants besides 
those which gather it? 

27. Since all rainfall comes from the water vapor in the air and 
the water vapor comes chiefly from evaporation of ocean water, how 
do the interiors of continents get their rain? 

28. Under a thick covering of snow, meadows and wheat fields re¬ 
main green throughout the winter, though air temperatures fall 
much below freezing. Why is this? 


REVIEW QUESTIONS 11 

29. (a) What is the relation of the dust in the air to twilight and . 
dawn? (6) To our ability to see objects not receiving direct 
sunlight ? 

30. (a) How are some plants dependent upon the dust in the air? 
(6) How are some diseases related to it? (c) How putrefaction and 
fermentation? 

31. (a) How is dust related to rainfall? (6) How is it related to 
the color of the sky? (c) To the color of the sun at rising and 
setting ? 

32. (a) According to the nebular hypothesis what is the origin of 
the air? ( b ) What, according to the planetesimal hypothesis? 

33. What is the probable future of the air? 


CHAPTER VII 

TEMPERATURE OF THE AIR 

1. Give six reasons for thinking that the sun is the chief source 
of our heat. 

2. (a) How do we know that we receive heat from the interior of 
the earth? (6) If this were the chief source of heat, what part of 
the earth would be hottest? Note. A hot iron ball suspended in 
air will radiate its heat in every direction until it has the temperature 
of the surrounding space. 

3. Why do we conclude that the interior of the earth is “ intensely 
hot ”? Why do we think outer space is “ intensely cold”? Note. 
Airplane flights into high altitudes show that the air does not con¬ 
tinue indefinitely to grow colder, but a little above seven miles the 
temperature remains about constant. 

4. (a) What is insolation? (6) What part of insolation is trans- - 
formed into heat? (c) What is heat? 

5. (a) When insolation is received, how is it disposed of? ( b) 
Give in tabular form the relative ways in which air, land, and water 
dispose of insolation. 

6. Why is a land area more heated by insolation and more 
cooled when insolation is withdrawn than a water area alongside? 

7 (a) Will a house painted red be warmer or cooler in winter 
than a house painted white? ( b ) Which will be the warmer in sum¬ 
mer? (c) Why do the inhabitants of hot countries wear light- 
colored clothing? 


12 


REVIEW QUESTIONS 


8. Why will a kettle of hot water remain hot longer after removal 
from the fire if the kettle is polished than if the kettle is unpolished ? 

9. (a) Explain the distribution of heat by conduction, by con¬ 
vection, and by radiation. (6) Give examples of distributing heat 
by each process. 

10. Why do we heat our kettles from below? Why could we not 
economically heat them from above? Note. Water is heaviest at 
39°F., becoming lighter when either heated above or cooled below 
that temperature. 

11. Why do shallow lakes'freeze more quickly than deep lakes? 

12. The temperature of the deep waters of the Great Lakes is 
39° F. Why? 

13. Why are heating plants in buildings usually placed at a lower 
level than the rooms to be heated? 

14. Why do we place the heating apparatus in our rooms near the 
floor instead of near the ceiling, where it would be less in the way? 

15. Why does the air warm up faster than it cools down? 

16. Why is the lower air more heated and more cooled than the 
air at higher levels, and why is the air at high levels always cold ? 

17. Why is the hottest time of the day after the hour when insola¬ 
tion is most intense, and the coldest hour near sunrise instead of 
midnight ? 

18. Describe the construction of a mercurial thermometer. May 
the same thermometer be both an F. and a C. thermometer? 

19. What makes the mercury rise? What makes it fall? 

20. Why should the thermometer tube be of even bore? 

21. (a) What is the purpose of the bulb of the thermometer? ( b ) 
If there were no bulb, would the instrument be a thermometer? 

22. Many thermometers have a cylindrical instead of a spherical 
bulb. What is the advantage of one over the other? 

23. (a) Why are alcohol thermometers necessary in polar regions 
instead of mercury thermometers? (6) Why is mercury better than 
alcohol in thermometers for high temperatures? 

24. Convert the following C. readings to F.: 50°, 40°, 30°, and 10°; 
the following F. readings to C.: 32°, 50°, and -4. 

25. What are maximum and minimum thermometers? 

26. (a) Describe the maximum thermometer. ( b ) What practical 
use is made of the maximum thermometer? (c) Make a drawing of 
a maximum thermometer. How is it adjusted for a new reading? 

27. (a) Describe the minimum thermometer. ( b ) Why is it made 
with alcohol? ( c) Why cannot it be hung in a vertical position as an 
ordinary thermometer? (d) How adjust it for a new reading? 


REVIEW QUESTIONS 13 

28. (a) What is a thermograph? (6) Does it take the place of 
the maximum and minimum thermometers? (c) From the thermo¬ 
graph record — thermogram — at what time does the maximum 
temperature usually occur? ( d ) At what time does the minimum 
temperature occur? 

29. How can we get the average temperature for a day? For a 
week? For a year? 

30. (a) What is meant by the temperature range for a given time? 
(6) From a thermogram find the temperature range for some day. 

31. (a) Give the chief factors that determine the distribution of 
insolation over the earth. (6) Which of these factors are uniform 
along a parallel of latitude ? 

32. What is the relation between the length of the continuous 
insolation period and latitude (a) in the summer hemisphere? (6) In 
the winter hemisphere ? 

33. (a) What is the date of the longest insolation period in the 
United States? (b) What is its date in Australia? (c) Give the 
dates of shortest insolation period in these two countries. 

34. (a) How does the angle of insolation vary through the day? 
(6) At what hour are we receiving most insolation? 

35. (a) How does the angle of noon insolation vary at London 
during the year? (b) When is it greatest there? 

36. Why is not the angle of insolation the same for all places at 
any time? 

37. (a) Why does the angle of noon insolation vary at any place? 
(b) How much does it vary at places outside the tropics? 

38. Describe the change in the angle of noon insolation during the 
year at a place within the tropics. 

39. (a) What places have vertical insolation once during the year? 
(6) What places have vertical insolation twice? What must be the 
latitude of a place in order that it may never have vertical insolation? 

40. In general how is the amount of insolation related to the angle 
of insolation? 

41. (a) How does the condition of the air as to clouds and dust 
affect the amount of insolation received? (b) Why is more insola¬ 
tion received on a mountain top than in the adjacent valley? 

42. Why are oblique rays from the sun less intense than vertical 
rays? (See page 101.) 

43. (a) What is the greatest difference in distance from the sun of 
two places receiving insolation at a given time? (b) What is the 
difference in distance of any place on the earth from the sun at 
perihelion and at aphelion? (See page 102.) 


14 REVIEW QUESTIONS 

44. Name factors that affect the distribution of heat, but not of 
insolation, over the earth. 

45. Make a general statement (a) of the relation of the distribution 
of land and water to the distribution of heat over the earth; (6) of 
the relation of temperature to altitude. 

46. How explain the low temperatures of polar regions even during 
the long summer day? 

47. Why is air at altitudes above a few thousand feet always cold? 

48. Define “ doldrum belt ” and “ heat equator.” 

49. Why does the heat equator shift? 

50. What determines whether the air is warming up or cooling 
down ? 

51. (a) Why is the hottest time of day after twelve o’clock? 
( b ) The hottest time of the year after the date of the summer 
solstice? 

52. Why does the heat equator shift more over the Atlantic than 
over the Pacific Ocean? 

53. Why is the average position of the heat equator north of the 
terrestrial equator? 

54. (a) What are isotherms? ( b ) Why do isotherms have a gen¬ 
eral east-west trend? Why are they not due east-west lines? 

55. Why may isotherms not intersect? May the heat equator 
intersect an isotherm? 

56. What is meant by temperature gradient? (See page 107.) 

57. How are the isotherm through any place and the temperature 
gradient at that place related in direction? 

58. (a) What is an isothermal chart? (6) How are steep and 
gentle temperature gradients shown on such charts? 

59. What instrument gives us a “temperature curve”? 

60. (a) What is meant by vertical temperature gradientf (6) 
What is its average value at low altitudes? 

61. Why do we find higher temperatures over Australia, Africa, 
and South America in January than over the oceans in the same 
latitude? 

62. Why is the winter in the northern hemisphere so much colder 
than that in the southern hemisphere ? 

63. Why do the isotherms for January in the northern hemisphere 
bend southward in crossing the continents, whereas in July they 
bend northward ? 

64. (a) Why is the temperature of Denver more equable than that 
of St. Louis? (6) Chicago more equable than Minneapolis? (c) 
Atlantic City more equable than Pittsburgh? 


REVIEW QUESTIONS 15 

65. How can the thermometer be used to determine approximate 
altitude in a balloon .or airplane flight ? 

66. (a) Why do plants put forth their leaves earlier on south slopes 
than on north slopes of land in the United States? (6) Would it be 
the same in Argentina? 

67. Why is a cloudy day in winter warmer and in summer cooler 
than a clear day? 

68. Why is it warmer in summer in St. Louis than at the equator ? 


CHAPTER VIII 

WEIGHT AND DENSITY OF THE AIR 

1. Why are we not conscious of the pressure of the air? 

2. What is the pressure of the air at sea level, (a) per square inch, 
(6) per square foot, (c) per acre? 

3. How long a column (a) of mercury, (6) of fresh water, (c) 
of sea water will the air sustain at sea level ? 

4. How is the sustaining or balancing power of the air used in 

(а) the lifting pump, (6) the siphon, (c) the barometer? 

5. (a) What does a cubic foot of air at sea level weigh? (6) What 
weight of air is in your bedroom, (c) your classroom? 

6. Why does a cubic foot of air weigh more at sea level than at 
higher altitude ? 

7. What is meant by the terms density and volume f What rela¬ 
tion exists: ( a ) between pressure and density, ( b ) between pressure 
and volume t 

8. How high would we have to ascend to leave half of the weight 
of the air below us? What part of the air would be below us if we 
ascended twice as high? 

9. (a) Define barometer. (6) Explain the principle underlying 
the construction of both the mercurial barometer and the aneroid 
barometer. 

10. (a) Give the essential construction of the mercurial barometer. 

(б) Why is it necessary to have some space in the tube above the 
column of mercury? (c) Why is it necessary that this space should 
be a vacuum? 

11. (a) What sustains the column of mercury in the tube? (5) 
How long a column of mercury is normally sustained at sea level? 
(c) Why is this column shorter the higher we ascend? 


16 REVIEW QUESTIONS 

12. In what unit do we ordinarily read the barometer in the 
United States? 

13. (a) Why is it necessary to hold the mercurial barometer in a 
vertical position when taking a reading? (6) How rapidly does the 
barometer fall as we ascend with it above sea level? 

14. (a) Describe the essential construction of the aneroid barom¬ 
eter. (6) What scale besides the one measuring pressures is often 
found on an aneroid barometer? (See page 118.) 

15. Why is the rate of fall of the barometer not uniform as it is 
carried up in the air ? 

16. Why does the barometer vary at any place from hour to hour? 

17. (a) What is a cyclone or low? (6) An anticyclone or high? 

18. (a) What is an isobar? (6) What is pressure gradient? (c) 
What is the relation in direction of the isobar and pressure gradient 
at any place? 

19. In what sense is a high an atmospheric hill, and a low an 
atmospheric basin? 

20. How does the spacing between isobars indicate the pressure 
gradient? 

21. Define (a) barograph; ( b ) pressure curve, or barogram. 

22. Why are pressures upon the earth in roughly east-west belts? 

23. (a) Explain the low-pressure doldrum belt; (b) the high- 
pressure horse-latitude belts, (c) Give their approximate latitude 
positions. 

24. Why do the pressure belts shift? 

25. How can the barometer be used to determine altitude? 

26. Explain why pressure increases with increase of temperature 
in closed vessels filled with air, whereas in the open air pressure 
decreases with increase of temperature. 

27. What is meant when we say the pressure of the air is 30 inches? 

28. Why is it not necessary to hold an aneroid barometer in any 
special position? 

29. Why is it not necessary that the bore of the barometer tube 
be uniform as in the thermometer? 

30. What is the general relation between barometer change and 
change in the thermometer? 

31. (a) Why is mercury so generally used in the construction of 
liquid barometer? (6) Could we have a water barometer? 

32. Why do standard barometers have a thermometer attached? 


CHAPTER IX 

MOVEMENTS OF THE AIR 

1. (a) Define wind, (b) Distinguish between winds and currents. 

2. (a) What is the cause of winds? ( b ) How does the air move 
above a heated area? (c) How does the air move about a heated 
area ? 

3. Why does a heated area become a low-pressure area? 

4. (a) What is meant by terrestrial windsf (6) Name the belts 
of winds and calms that constitute the terrestrial winds. 

5. (a) What and where is the doldrum belt? (b) Why is it a 
low-pressure belt? 

6. (a) What are the trade winds, and why are they so called? 
(6) Between what approximate latitude limits do the trade winds 
lie? 

7. (a) What are the horse latitudes ? (b) In about what latitudes 
are the horse latitudes? (c) Why are the horse-latitude belts called 
calm belts? 

8. (a) Why are the horse latitudes high-pressure belts? (6) How 
does the air move above the horse latitudes? (Above does not mean 
north of.) 

9. Why do the trades and prevailing westerlies blow out from the 
horse-latitude belts? 

10. Why are the doldrums and horse latitudes belts rather than 
areas? Why do the winds blow in toward the doldrum belt from 
either side? 

11. (a) State Ferrehs Law. (b) How does this law account for 
the oblique movement of the trades and prevailing westerlies with 
reference to the pressure belts? 

12. Give the two important laws governing winds. 

13. By means of Figure 56 explain deflection of winds from a 
straight course, or the pressure gradient. 

14. Since winds moving into regions of either less or greater rota¬ 
tional velocity are deflected from the gradient, where and in what 
directions could a wind blow upon the earth and not suffer deflection? 

15. What is meant by the circumpolar whirls? Give the direction 
of this whirl in each hemisphere. (Where winds suffer a deflection to 
the right and crowd in toward a center, a left-handed or counter¬ 
clockwise whirl is developed, and where deflection is to the left a 
clockwise whirl is developed.) 


17 


18 


REVIEW QUESTIONS 


16. (a) Why do the calm and wind belts shift? (6) What are 
monsoon winds? (c) How many monsoon belts of wind are there? 
(d) Where do they lie? 

17. (a) Explain the hooked trades. ( b ) With what winds do the 
hooked trades north of the equator alternate? (c) With what winds 
do the hooked trades south of the equator alternate? 

18. Of what winds are the hooked trades both north and south of 
the equator continuations? 

19. Why are the monsoons of the Indian ocean the best developed 
of all on the earth? 

20. Why are the circumpolar winds stronger, in winter than in 
summer ? 

21. Why are the northern Pacific and Atlantic low-pressure areas 
in winter? (The North Pacific is the region which probably gives 
rise to our winter cyclones that move southeastward into northwest 
America.) 

22. Since the continental air drifts are so easily concealed by the 
other classes of winds, how is their existence manifested? 

23. Why are the polar areas thought to be low-pressure regions? 

24. (a) Explain land and sea breezes. ( b ) About what hour does 
the sea breeze arrive? (c) Why are not land and sea breezes devel¬ 
oped every day? 

25. (a) Explain mountain and valley breezes, (b) When does 
each blow? 

26. The trade winds are constant winds and the monsoons are 
periodic. What is the significance of these terms as applied to these 
winds ? 

27. What are cyclonic windst Why are cyclonic winds called 
unperiodic? 

28. (a) Why do highs and lows drift eastward in the United 
States? ( b ) What direction do they move in Argentina? (c) In 
the trade-wind belts ? 

29. Using Figures 61 and 62, describe the movement of the winds 
(a) about highs in the northern hemisphere and ( b ) about lows in 
the northern hemisphere, (c) How would the winds move about 
highs and lows in the southern hemisphere? 

30. What is meant by a convectional low? Explain driven cyclones 
and frictional cyclones. 

31. Name the four distinct movements of the air in and about 
a low. 

32. Give the three customary paths followed by lows in the United 
States, and tell where those following each path originate. 


REVIEW QUESTIONS 19 

33. (a) Upon what does the direction of a wind at any place and 
time depend? ( b ) Explain a north wind. (See page 130.) 

34. (a) Upon what does the velocity of a wind depend? (6) Why 
does the velocity of the wind increase as we near the center of a low 
and decrease as we approach the center of a high? 

35. In what latitudes do cyclonic winds prevail? (See page 130.) 

36. (a) Define tornado, hurricane, and typhoon. ( b ) In what 
particulars do these three storms differ? 

37. (a) What is the eye of the storm in tropical cyclones? (6) 
How do you explain it? (Where the storm is intense and of wide 
extent the air at the center of the area is descending.) 

38. (a) Why does the wind shift or change in direction at any 
place? (6) Give the direction of shifting when a low passes north of, 
directly over, and south of a place; also when a high passes in similar 
fashion. 

39. In like manner consider the direction of shifting in the north- 
westerlies of the southern hemisphere. 

40. (a) About what is the change of temperature with change of 
latitude? (6) With change of altitude? '(c) Why does rising air 
cool, and how fast? 

41. (a) Why are winds moving poleward warm winds and those 
moving toward the equator cold winds? ( b) Why are rising air 
currents warm and descending currents cold? (c) Why does descend¬ 
ing air become warmer? 

42. (a) Locate and describe the hot wave, the sirocco, the simoom, 
the Chinook and the foehn. ( b ) Explain the effect of each. 

43. Describe the norther and the blizzard, giving the location of 
each with characteristics. 

44. (a) By what instrument is the velocity of the wind measured? 
(6) In what unit is the velocity of the wind measured? (c) Give the 
approximate velocity of a light breeze, a brisk wind, of a gale. 

45. (a) Why does the wind blow? (6) Why is there not always 
wind ? 

46. (a) Why are summer days, as a rule, more apt to be windy 
than summer nights? (6) Than winter days? 

47. Why are trade winds, as a rule, stronger than westerlies? 

48. Why are upper currents stronger than surface winds, and 
winter winds stronger than summer winds? 

49. Why are the upper currents in all latitudes from a westerly 
quarter? 

50. Why are storms that come from the southwest often called 
northeasters? 


CHAPTER X 

MOISTURE OF THE AIR 


1. (a) What is water vapor? ( b ) Define evaporation. 

2. Upon what does the amount of water in the air chiefly depend? 

3. (a) At what temperatures does evaporation take place? (6) 
Define vaporization. 

4. What is it we see issuing from a boiling kettle? 

5. Define: (a) absolute humidity, ( b ) relative humidity, (c) 
capacity, and (d) saturation as applied to the air. 

6. What is meant when it is said the humidity of the air is 60 per 
cent? 100 per cent? (b) What is meant by dew point? 

7. (a) Define condensation as applied to the water vapor of the 
air. ( b ) Under what condition will condensation take place? 

8. How does increase of temperature of the air affect (a) evapora¬ 
tion, (6) absolute humidity of the air, (c) relative humidity of 
the air? 

9. (a) Name four ways in which the air may be cooled, (b) 
Which of these occurs chiefly in the day time? (c) Which chiefly 
at night? 

10. (a) Why does rising air cool? (6) At what rate does cooling 
of rising air go on? 

11. Explain the difference between convectional ascent and forced 
ascent. 

12. ( a ) Why is descending air warmed? (6) At what rate is it 
warmed ? 

13. Explain the abundant rainfall of (a) the doldrums, (6) the 
windward slopes of mountains, (c) low-pressure areas or cyclones. 

14. Explain the deficient rainfall of (a) the horse latitudes, (b) the 
trade-wind belts, (c) the leeward slopes of mountains, (d) high- 
pressure i areas or anticyclones. 

15. What determines whether the result of condensation of water 
vapor shall be liquid or solid? 

16. Give examples of evaporation of ice without melting. 

17. Explain how evaporation is a cooling process; that is, that it 
. cools objects in the vicinity of the evaporating substance. In like 
manner explain how condensation is a warming process. 

18. (a) What is latent heat? (6) How does it differ from sensible 
heat? 


20 


REVIEW QUESTIONS 


21 


19. Why will a dry bulb thermometer held in front of a rapidly 
revolving fan show an increased temperature and a wet bulb ther¬ 
mometer held in like position show a decreased temperature? 

20. (a) How does fanning cool one’s face or hands? (b) Why are 
we so easily chilled in wet garments? 

21. (a) Describe and explain the principle of the psychrometer. 
( b ) Under what condition will the wet and dry bulb thermometers 
show the same reading? 

22. (a) What does a wide difference in the reading of the wet and 
dry bulb thermometers indicate? (6) What does a small difference 
indicate? 

23. Why is a burn from steam more severe than a burn from 
boiling water? 

24. Explain how exposing pans of water in a room where growing 
plants are kept may prevent freezing temperatures occurring in the 
room. 

25. (a) Why is there more water vapor in the lower air than in 
the upper air? (6) Why more over the sea than over the land? ( c ) 
How is water vapor distributed in the air? 

26. Why does relative humidity usually increase with increase of 
altitude in the day time, whereas at night it is often greatest at the 
bottom of the air? 

27. (a) At what hour of the day or night is relative humidity of 
the air highest? Why? (b) At what hour is it lowest? Why? 

28. (a) Explain dew and frost, (b) Why do not dew and frost 
usually occur on cloudy nights? (c) Why do they not usually occur 
on windy nights? 

29. Why are station platforms with a roof above them less likely 
to be covered with frost in winter than those without such shelter? 

30. Why is a metal roof more apt to be covered with frost than a 
wooden or paper roof? 

31. (a) What are cloudsf (b) Name four types of cloud and tell 
how they may be recognized. 

32. (a) How do cirrus clouds differ from the other types? (b) 
From which type do rain and snow fall? 

33. (a) Why are cumulus clouds more common in day time than 
at night? (b) Why are they more common over land than over 
the sea? 

34. (a) What is fog? (6) Why does it occur more often at night 
or in the early morning than during the day? (c) What becomes 
of fogs? 

35. (a) What is the explanation of the frequent and dense fogs 


22 


REVIEW QUESTIONS 


over the sea to the east and north of Newfoundland? (6) Why are 
these fogs particularly dangerous to travel and commerce? 

36. (a) Why is the western coast of the United States more foggy 
than the eastern coast? (6) Account for the frequent and dense fogs 
of London. 

37. Why do fogs gather more frequently and earlier in the evening 
over lakes and in valleys than on adjacent uplands and mountain 
slopes? 

38. (a) Explain rain and snow. (Much precipitation that falls 
as rain is really melted snow.) ( b ) What is the snow line? (c) 
Upon what does the altitude of the snow line depend? 

39. (a) Explain the formation of sleet and hail. ( b ) Why is hail 
usually a summer phenomenon? (c) How do you account for the 
large size of many hailstones? 

40. (a) Explain sheet ice. (6) How does sheet ice differ from 
sleet? (c) Explain why sheet ice is destructive to streets and tele¬ 
phone and telegraph lines. 


CHAPTER XI 

LIGHT AND ELECTRICITY OF THE AIR 

1. (a) Why does the sun not always appear the same color? 

(b) At what times of the day is it most likely to appear yellow or 
orange-colored ? Why ? 

2. (a) What is light? ( b ) How does it come to us from the sun? 

(c) How fast does it travel? 

3. (a) How does blue light differ from red as to wave length? 
(6) What effects due to this difference in wave lengths are observed 
when sunlight passes through dusty air? 

4. (a) Why is the sky blue? (6) Why is it a deeper blue after a 
rain or snowstorm? (c) Why is the sky a deeper blue over the sea 
than on land? ( d ) On a mountain top than at its base? 

5. Why might we expect the stars to appear, even while the sun 
shines, if we could ascend high enough in the air? 

6. (a) What is refraction as applied to light? (b) What two 
things are necessary to refraction of a ray of light ? 

7. (a) How is a ray of light bent in passing from a rarer to a 
denser medium? (6) From a denser to a rarer medium? 

8. (a) What is meant by the terms angle of incidence and angle 


REVIEW QUESTIONS s 23 

of refractionf ( b ) In Figures 76 and 77 indicate these two angles, 
of incidence and refraction . 

9. (a) Why do the sun, moon, and stars seem higher above the 
horizon than they really are? ( b ) Where would a star have to be 
situated so as not to be displaced by refraction? 

10. (a) Why do fish in a clear pool or stream appear nearer the 
surface than they really are? (b) If a rifle were aimed directly at a 
fish, would the ball hit it? 

11. (a) What is the effect of refraction of the sun’s rays upon the 
length of the period of sunshine? (6) Where is this effect the 
greatest ? 

12. (a) When viewed from a mountain top, why do other moun¬ 
tain peaks appear higher than they really are? (6) As seen from a 
balloon, why does the landscape below appear bowl-shaped? 

13. (a) What is looming? (6) What are the conditions that make 
looming possible? (c) Why do we not usually see looming at mid¬ 
day? ( d ) Would rising in the air effect the phenomenon of looming? 

14. (a) What is total reflectionf ( b ) In Figure 80 indicate the 
“ critical angle.” '(c) What is meant by critical angle? 

15. (a) What are the conditions that make possible the phenome¬ 
non of hot weather mirage? ( b ) Are both object and reflection 

visible in this phenomenon? 

16. (a) What conditions are necessary for cold weather mirage? 
(6) What is the position of the reflection in this phenomenon? Is 
the object necessarily visible? 

17. (a) What is dispersion of light? ( b ) What causes the disper¬ 

sion of the colors? 

18. (a) Explain halos. (5) What is the arrangement of the colors 
in halo rings? (c) Is the phenomenon of-colored rings about street 
lights when seen through foggy air analogous to solar and lunar halos? 

19. (a) What is the explanation of the rainbow ? ( b ) Under what 

conditions may the rainbow be seen? (c) What is the order of the 
colors in the rainbow? (d) Is it the same as in the halo? 

20. ( a ) Are the colored rings seen in the spray of a waterfall or a 
fountain the same phenomenon as the rainbow? (b) On which side 
of a playing fountain should you stand at noon to see the rainbow 
in the spray? (c) Would it be the same in Buenos Aires? 

21. (a) What is the explanation of the secondary bow? (6) What 
is the order of the colors in this bow ? 

22. (a) In what direction would you see the rainbow in the 
morning? ( b ) In the evening? (c) Why do we so rarely see a 
rainbow at noon? 


24 REVIEW QUESTIONS 

23. (a) What is lightning? (6) What is thunder? (c) Why are 
thunderstorms most common in the afternoon and in summer? 

.24. (a) Why are trees and buildings more apt to be struck by 
lightning than an animal in the vicinity of the lightning flash? ( b ) 
Why are lone trees more often struck than trees in a forest ? 

25. (a) What is the principle of the lightning rod? (6) Why is it 
necessary that it extend into the ground? 

26. (a) What is the relation of lightning to rain? (6) Why do 
lightning flashes cease soon after rain begins to fall ? 

27. (a) What is the aurora? ( b ) Is there a similar phenomenon 
to the aurora borealis in the southern hemisphere? (c) Why is the 
aurora not seen in the tropics ? 

28. What reason have we for thinking the aurora is electrical in 
its character? 


CHAPTER XII 

WEATHER AND CLIMATE 

1. (a) What is weather? (h) What is climate? (c) When do 
you speak of weather, of climate ? 

2. (a) What are the weather elements? ( b ) Which do you con¬ 

sider most important, and why? 

3. (a) How does temperature ordinarily vary through the day 
and why? (6) About what hour of the day is the temperature 
usually highest? Lowest? Why? 

4. (a) How does the humidity change with change of tempera¬ 
ture? (5) At about what hour is humidity highest? Lowest? 
Why? 

5. Why do we not notice changes in the 'pressure of the air, since 
it is one of the most important weather elements? 

6. What are the most important weather controls? 

7. How are weather changes related to (a) altitude, (6) distance 
from the sea, (c) latitude? 

8. (a) Why does the absolute humidity ordinarily increase during 
the day, whereas the relative humidity decreases? (6) Why is 
relative humidity higher at night? 

9. (a) Why are convectional cyclones more frequent over the 
land than over the water? (6) Why more vigorous in summer than 
in winter; in day time than at night? 


REVIEW QUESTIONS 


25 


10. Why are convectional cyclones more frequent and intense in 
summer, and nonconvectional cyclones more frequent and intense in 
winter ? 

11. Why do cyclones usually continue longer over the sea than 
over the land? 

12. Why, in springtime, do we often have blustery days followed 
by calm nights? 

13. What justification is there for the saying, “ Night is the winter 
of the tropics ”? 

14. Account for (a) the high temperature, ( b ) low pressure, and 
(c) the abundant and daily rains of the doldrum belt. 

15. Account for (a) the constancy of the winds, both in direction 
and strength, and ( b ) the scant rainfall of the trade-wind belts. 

16. Under what conditions do rains occur in the trade-wind belts? 
Give an example. 

17. (a) What is the explanation of the monsoon changes of weather 
on the margins of the trade-wind belts? (b) Recount these changes. 

18. What is meant by the expression “ the weather of the prevailing 
westerlies is of cyclonic control ” ? 

19. Why is there greater regularity in weather changes in the belt 
of prevailing northwesterlies than in that of the prevailing south- 
westerliesf 

20. What are the “ Roaring Forties ” and what is their explanation? 

21. How are we able to predict the weather with about 85 per 
cent verification? 

22. Why is weather prediction easier and less important in the 
doldrum and trade-wind belts than in the belts of the westerlies ? 

23. For worth-while weather prediction, what controlling con¬ 
ditions must be taken account of? 

24. Why do cyclones in the United States move eastward? Note. 
They move generally southeastward west of the Mississippi River 
and northeastward east of it. 

25. (a) Why do the winds about a cyclone center move toward 
that center; and (6) why in the northern hemisphere do winds spiral 
about the center counterclockwise? 

26. Why are the isotherms through a cyclonic area warped into a 
northeast-southwest direction? 

27. Why are temperatures in front of a low warmer than in the 
rear of the low? 

28. Why does the cloudy area and area of precipitation extend 
farther in front of than in rear of the low ? 

29. What prediction as to (a) change of temperature, (6) change 


26 REVIEW QUESTIONS 

in state of sky, and (c) change in strength of wind with an approach¬ 
ing low? 

30. (a) From what direction do lows approach? (6) What would 

be the prediction as to weather changes with a receding low? (c) In 
what direction do lows recede? 

31. Why are passing lows associated with cloudy skies and precipi¬ 
tation? 

32. Why do we ordinarily have winds increasing in strength as a 
low approaches and decreasing in strength as a low recedes? 

33. (a) What is a cold wave, and under what conditions are they 
apt to occur? (6) What is a blizzard? 

34. (a) How do “ highs ” move across the United States; and 
( b ) how do the winds move about a high? 

35. Why do cooler temperatures precede and warmer temperatures 
follow the passage of a high across the United States? 

36. (a) Why are highs usually areas of clear skies? (b) If clouds 
appear, why are they apt to be in the rear of the high? 

37. (a) Why do the winds weaken upon the approach of a high 
and strengthen as the high recedes? (b) from what direction do 
highs usually approach? 

38. {a) Why do thunderstorms occur in association with lows 
rather than with highs, and (6) why are they usually southeast of 
the low center? 

39. Why does the lightning in the thunderstorm so quickly cease 
after the rain begins to fall? 

40. (a) Why is hail so commonly associated with thunderstorms? 
(b) Why are thunderstorms usually daytime and summer phe¬ 
nomena ? 

41. (a) What is a tornado? How does it differ from a cyclone? 
(b) Where in the United States are tornadoes most frequent, and 
during what months? 

42. (a) In what direction do tornadoes usually progress in the 
United States? (6) What means are used in western United States 
to protect from tornadoes? 

43. (a) How fast do tornadoes ordinarily advance? (6) How wide 
is their path of destruction? (c) How strong are the winds some¬ 
times noted about them? 

44. Why are tornadoes more frequent in the Mississippi Valley 
states than in the Rocky Mountain or Appalachian Mountain states? 

45. (a) What is the United States Weather Bureau? (b) To what 
department of the Government does it belong? (c) What is its 
business ? 


REVIEW QUESTIONS 


27 


46. (a) What weather conditions are shown on the weather map f 
(6) How are the data of the weather map got together? (c) What 
instruments are needed? 

47. (a) At what hour are the observations for the weather map 
taken? (6) Where is the weather map published? (c) What pur¬ 
poses does the weather map serve? 

48. Why is the weather map of greater importance to the Atlantic 
than to the Pacific Coast regions? 

49. (a) Name classes of people benefited by having the weather 
map, and (6) tell in what ways they are benefited. 

50. Give the scientific basis of the following weather proverbs: 
“Rainbow in the morning sailor’s warning; rainbow at night 
sailor’s delight.” “ Mackerel scales and mares’ tails, make lofty 
ships carry low sails.” “ Mist rising o’er the hill, brings more water 
to the mill.” 

51. (a)'What are the boundaries of the climatic zones? (6) Why 

are these boundaries different from the boundaries of the light zones? 

52. Why is the north temperate climatic zone wider than the south 
temperate ? 

53. Account for the heavy forests and dense jungles of equatorial 
South American, equatorial Africa, and the East Indies. 

54. Account for the desert climate of the Sahara and of central 
and western Australia. 

55. Account for the rainy climate of eastern Australia, southeastern 
Africa, eastern Brazil. 

56. Account for the dry climate of Peru, of the western coast of 
Mexico, and of Nevada. 

57. Account for the bracing climate and light rainfall of the horse- 
latitude belts. 

58. Account for the rainy climate of the Pacific Coast of northern 
United States and Canada and of Chile. 

59. (a) Why are low-lying land areas in the trade-wind belts 
likely to be desert? ( b ) Why are the southern coasts .of the moun¬ 
tainous islands of the West Indian and Hawaiian groups of islands 
dry? 

60. Account for the rainy climate of the eastern slopes of the 
Sierra Madre Mountains of Mexico and of the eastern Andes slopes 
of Peru. 

61. Explain the monsoon character of the climate of India. 

62. (a) Why are the western coasts in the belts of westerlies more 
uniform in climate than the eastern coasts? (b) Why are the eastern 
coasts more uniform than the interiors? 


28 


REVIEW QUESTIONS 


63. (a) In what way does the Gulf Stream influence the climate of 
the coasts it washes, and ( b ) what coasts are affected by this stream? 

64. Explain the climatic influence of (a) the Japan Current, (6) 
the Chilean Current, (c) the Labrador Current. (See Ocean Currents.) 

65. (a) What are the Polar Cold Caps? ( b) What are their chief 

climatic characteristics? (c) Why is the Antarctic cap larger than 
the Arctic? 

66. (a) What is meant by continental and marine climates? ( b) 
Why are marine climates less variable than continental? 

67. (a) What are the distinguishing characteristics of mountain 
climatesf ( b ) What is the chief difference in climates on windward 
and leeward sides of mountains? 

68. (a) Why do continent interiors have their greatest amount of 
rainfall in summer ? ( b) Why does the western coast in the westerlies 
have more rainfall in winter than in summer? 


CHAPTER XIII 

CLIMATE OF THE UNITED STATES 

1. The two outstanding climatic characteristics of the Pacific 
Coast of the United States are equable temperature and winter rains. 
Explain. 

2. (a) Why is the Great Basin of western United States dry? 
( b ) What is the source of the small amount of rain it receives? (c) 
Explain its extremes of temperature. 

3. The 100th meridian west marks approximately the boundary 
line between profitable and unprofitable agriculture by ordinary 
methods. Explain. 

4. (a) Why are the lands between the Rocky Mountains and the 
Mississippi River so largely prairie? (6) What are the chief agri¬ 
cultural products of these prairies? 

5. Account for the increasing rainfall eastward from the Missis¬ 
sippi River to the Appalachian Mountains and the heavy snowfall of 
the Great Lakes region. 

6. (a). Why is the Atlantic Coast of the United States more 
varied in climate than the Pacific Coast? (b) What two ocean cur¬ 
rents affect this coast? (See Ocean Currents.) 

7. (a) Describe the course of tropical cyclones originating in the 
West Indies. (6) At what season of the year are they most frequent? 


REVIEW QUESTIONS 29 

8. Why does Boston have a greater number of cyclonic dis¬ 
turbances than any other city of its size in the United States? 

9. Name three cities with distinctly winter rains, three with dis¬ 
tinctly summer rains, and three with rain distributed pretty uni¬ 
formly through the year. 

10. Locate and explain the greatest rainfall and the least rainfall' 
in the United States. 

11. (a) From what direction do storms in your section usually 
come? (6) What direction of wind is most apt to bring snow in 
winter and rain in summer? 

12. (a) What direction of wind is usually coldest? ( b ) Warmest? 
(c) Most apt to be accompanied by fog? 


CHAPTER XIV 

GENERAL CHARACTERISTICS OF THE SEA 

1. What important advantages to cities arise from location near 
the sea? 

2. Distinguish between sea, ocean, and lake. (See page 443.) 

3. What effect do continental and mountain masses have upon 
the level of the sea along their borders? Give examples. 

4. Compare the areas and the lengths of shorelines of the Atlantic 
and Pacific Oceans. 

5. Describe conditions about the south pole that make it less 
accessible than the north pole. 

6. Where and what is the greatest known depth of the sea? 

7. (a) What is the average depth of the sea? (6) The average 
altitude of the land? 

8. If all the land above sea level were carried into the sea, would 
there be enough of it to fill the ocean basins? 

9. How many pounds of common salt are there in a hundred 
pounds of sea water ? 

10. ( a ) How do the gases, oxygen and carbon dioxide, get into sea 
water? (6) What use is made of them? 

11. (a) Why are not all parts of the sea equally salty? (6) Where 
is sea water most salty? (c) Where least? 

12. Account for the low temperature of deep ocean waters. 

13. What economic and what scientific information has been ob¬ 
tained by sounding and dredging? 


30 REVIEW QUESTIONS 

14. Why is the ocean floor in general smoother than the surface of 
the land? 

15. How do you account for islands in the ocean near continents? 
In mid-ocean? 

16. (a) What is the continental shelf? (6) Compare its widths 
along the eastern and western coasts of the United States. 

17. Compare the deposits of the continental shelf with the oozes 
beyond its limits. 

18. (a) State the sources of the deposits in the “ deeps ” of the 
ocean. (5) What evidence have we that these deposits accumulate 
very slowly? 

19. (a) What is the difference in origin of an iceberg and an ice 
floef ( b ) Where do the icebergs of the North Atlantic come from? 
(c) In what ways are they a menace to ships? 

20. State reasons for the greater abundance of life on the conti¬ 
nental shelf than in mid-ocean. 

21. Consult Figure 102, and account for the more southerly and 
easterly of the limit of drifting ice in the northern hemisphere in 
summer. 


CHAPTER XV 
MOVEMENTS OF THE SEA 

1. (a) A wave has been defined as a hill of water that comes 
toward you. What can you say in favor of this definition? (6) 
What can be said against it? 

2. Name the most important motions of ocean water, and state 
the cause of each. 

3. How does the direction of motion of the wave compare with 
the direction of the wind? 

4. If we were to dye a certain wave red as it passed our boat, 
should we be able to identify the wave when it passed the boat that 
was following us? Explain. 

5. (a) When swimming beyond the breakers, are you carried 
forward with the first wave that you meet? (b) In other words could 
you ride a wave to shore ? 

6. Distinguish between the motion of a wave and the motion of 
the particles of water that form the wave. 

7. Define crest, trough, height of wave, length of wave, ground 
swell, breaker, surf, and undertow. 


REVIEW QUESTIONS 31 

8. Why does the front of a wave become steeper as it approaches 
the shore? 

9. In what two ways do waves wear away a sea cliff? 

10. (a) How are sea caves formed? (6) How are beaches formed? 

11. Describe the formation of a sand reef, a sand spit, and a 
" hook.” 

12. Define tides, flood tide, ebb tide, tidal range, tidal race, bore. 

13. (a) What are spring tides? (6) Neap tides? (c) Why are 
both spring and neap tides more pronounced in the northern hemi¬ 
sphere during its winter than during its summer? 

14. Why is the tidal range greater in some harbors than on the 
open sea? 

15. What is the interval between two successive high tides?' 

16. What number of minutes is called the moon’s “ ear mark ” on 
the tides? 

17. (a) What is meant by the running of the tide ? ( b ) Why does 
the tide run in different directions at different times? 

18. What is meant by the establishment of a port? Why is this 
quantity important? 

19. State the economic importance of tides. 

20. (a) What provisions are made for docking ships in harbors 
with considerable tidal range? (5) Why does the tidal range vary 
from day to day? 

21. (a) The moon is considered the chief cause of the tides. ( b ) 
With our moon* going around the earth in about four weeks, how is it 
that we have two daily high tides ? 

22. When is a boat more likely to run aground during the low 
water of a spring tide or the low water of a neap tide? Explain. 

23. (a) What is meant by tidal scour? (6) What effect has this 
upon inlets? 

24. There are several important ocean currents in each of the 
oceans. Name some of them and specify whether warm or cold 
currents. 

25. Explain why the birthplace of ocean currents is located in the 
trade-wind belts. 

26. Why do the westward equatorial currents turn northward or 
southward ? 

27. How are the low temperatures of the deep equatorial seas 
accounted for? 

28. Why does the ocean current that warms British Columbia cool 
the coast of Mexico? 

29. What effects of the Gulf Stream are of great importance to 
many persons? 


32 REVIEW QUESTIONS 

30. Explain the semiannual reversal of the direction of the eddy 
in the North Indian Ocean. 

31. Why is the temperature of northern Norway so much warmer 
than that of Alaska in the same latitude ? 

32. Account for the (a) bleakness of Kamchatka and Labrador, 
the (6) fogs off Newfoundland, and (c) the coral rock of the 
Bermudas. 

33. Why does a portion of the South Equatorial Current cross the 
equator and join the Gulf Stream? 

34. Why do ships sailing from Honolulu to San Francisco take a 
more northerly route? 

35. Why do sailing vessels leaving New York for Rio Janeiro go 
so far over toward the African coast before crossing the equator? 

36. What route should you advise them to take on their return 
trip? 


CHAPTER XVI 

THE MANTLE ROCK 

1. Define rock, mantle rock, and bedrock. Give an example of 
each. 

2. What are the chief functions of the mantle rock? 

3. Name several kinds of mantle rock, and state their economic 
uses. 

4. Define weathering. 

5. Make a list of all the mechanical agents of weathering, and 
another of the chemical agents. 

6. Explain the difference between mechanical and chemical 
weathering. 

7. Under what climatic conditions is freezing and thawing most 
effective? 

8. ( a ) How does moisture aid weathering? ( b ) Wind-driven 
sand? (c) The oxygen of the air? ( d ) Change of temperature? 
(e) Gravity? (/) The carbon dioxide of the air? 

9. How does mantle rock retard weathering below the surface? 

10. Name several agents that transport mantle rock. 

11. Mention some mass of transported mantle rock, and name the 
agent that transported it. 

12'. Under what conditions does gravity transport mantle rock? 


REVIEW QUESTIONS 33 

13. (a) Describe the transportation of mantle rock by wind; 
(b) by waves. 

14. Name several characteristics of alluvial mantle rock. 

15. Name a common form in which seolian mantle rock is found. 

16. State the characteristics of glacial mantle rock. 

17. State and account for the differences between transported and 
residual mantle rock. 

18. Explain the origin of peat, and name a region where it is used 
as fuel. 

19. (a) How are sand dunes formed? (6) By diagram, show the 
leeward and the windward slopes of a sand dune. 

20. What means are sometimes used to check their forward move¬ 
ment? 

21. Name localities where sand dunes may be found. 

22. Briefly describe the method by which each of the following was 
formed: marl, humus, muck, silt, loess. 

23. (a) Define soil. ( b) Compare the characteristics of clay soils 
with those of loam; (c) with those of sandy soils. 

24. (a) Why are soils “ earlier,” or more responsive, on south-facing 
than on north-facing slopes; (b) when well-drained than when poorly 
drained ? 

25. What other conditions affect the earliness of soils? 

26. To what dangers of loss or deterioration is soil exposed? 

27. Mention measures that may be taken to conserve soil and to 
maintain its fertility. 


CHAPTER XVII 
THE BEDROCK 

1. Define mineral and explain the difference between minerals 
and rocks. 

2. Name four properties that aid in distinguishing minerals. 

3. Name four rock-making minerals, giving the principal distin¬ 
guishing characteristics of each. 

4. Give the essential composition of (a) granite, (b) sandstone, 
(c) shale, ( d) mica schist, (e) slate, (/) limestone. 

5. (a) Name three classes of rocks, based upon their origin. (6) 
Give an example of each class. 

6. In what parts of the United States are the bedrocks chiefly of 


34 REVIEW QUESTIONS 

(a) igneous origin, ( b ) of metamorphic origin, (c) of sedimentary 
origin? 

7. Give a theory as to rock salt deposits, and mention several 
localities where rock salt may be found. 

8. Arrange in tabular form the several kinds of rock waste being 
deposited upon the ocean floor, with the bedrock derived from each, 
and with its metamorphic equivalent. 

9. (a) What metals occur in the rocks in their pure state? ( b ) 
By what name are these metals known ? 

10. Name five important minerals used in the arts. 

11. Define ore, and give the name of an ore of each of the following 
metals: iron, copper, lead, zinc, tin, and mercury. 

12. By what characteristic features may each of the following be 
identified: (a) conglomerate, (6) shale, (c) limestone, ( d) granite, 
( e ) sandstone. 

13. Classify the following rocks as to origin: (a) sandstone, ( b) 
marble, (c) anthracite coal, ( d ) limestone, ( e ) basalt, (/) pumice, 
( g ) granite, ( h ) clay, (i) shale, (;) obsidian, (k) lava. 

14. (a) What is the significance of stratification in rocks? (b) 
How does this property aid in quarrying rocks ? 

15. How are the cleavage planes in slate produced? 

16. Why is the rock waste brought to the ocean assorted, and the 
different sized particles deposited in different places? 


CHAPTER XVIII 

STORIES IN STONE 

1. What is meant by “ stories in stone ”? 

2. (a) What are fossils? (6) Account for their occurrence in 
sedimentary rocks. 

3. How does the series of sedimentary rocks tell us the relative 
times when the different forms of life inhabited the earth? 

4. What sort of changes were used to divide the rock record into 
eras? 

5. What is the earliest form of plant life thus far found? 

6. What forms of life existed when the proterozoic rocks were 
being formed? 

7. What great change is shown in the life of the earth at the 
beginning of the paleozoic era? 


REVIEW QUESTIONS 35 

8. What was the highest type of life at the beginning of the 
paleozoic era? 

9. W 7 hat was the highest type in the middle of the paleozoic era? 

10. Describe the development of the eyes of the trilobites during 
the paleozoic era. 

11. What two forms of animal life appeared in the latter part of 
the paleozoic era? 

12. What conditions prevailed during the coal-forming period? 

13. Mention several events that tended to destroy much of the 
animal life at the close of the paleozoic era. 

14. (a) When did birds first appear? ( b ) What peculiar charac¬ 
teristics had they? 

15. Describe one of the great reptiles of the mesozoic era. 

16. (a) When did mammals appear? (6) Describe one of the 
early mammals. 

17. In what era did man appear? 

18. Show by diagram the order in which the different classes of 
life appeared upon the earth as indicated by fossils. 


CHAPTER XIX 
THE GROUND WATER 

1. What becomes of the rain? 

2. What conditions control the percentage of rain water evap¬ 
orated? 

3. How does evaporation affect the temperature of the air? 

4. Mention three factors that determine the percentage of the 
rainfall that sinks into the ground and becomes ground water. 

5. Define ground water, run-off, water table, water vapor, ad¬ 
hesion water, impermeable rock. 

6. Why is the water table sometimes horizontal and sometimes 
inclined ? 

7. What controls the direction of flow of the ground water? 
What force causes this motion? 

8. What action keeps the soil moist above the water table? 

9. How far down does the ground water extend? 

10. Name at least five ways in which the ground water returns to 
the surface. 


36 


REVIEW QUESTIONS 


11. Classify the kinds of work performed by ground water as 
constructive and destructive work. 

12. What conditions make erosion by ground water possible? 

13. What two substances found in bedrock are readily soluble in 
water? 

14. Name five deposits formed by ground water and five materials 
deposited by it. 

15. (a) Why are certain minerals deposited about springs? ( b ) 
About. geysers ? 

16. How are caves formed? 

17. Draw a diagram of a cave showing a sinkhole, stalactite, stalag¬ 
mite, and a pillar. 

18. Why are most caves formed in limestone regions? 

19. (a) Describe the forms of life in the Mammoth Cave. (6) 
How do they illustrate the adaptation of animals to their environ¬ 
ment? 

20. How are some natural bridges formed? 

21. (a) What is calcareous tufa? ( b ) How is it formed? 

22. Name four results of solution and deposition by ground water. 

23. Draw a diagram, and explain why some wells are permanent 
and others temporary. 

24. State the relation between the level of the water table near a 
well and the level of the water in the well. 

25. Name some of the sources of contamination of wells. 

26. (a) Describe the sanitary location of a well. (6) State two 
general laws governing the sanitation of wells. 

27. (a) What is an artesian well? ( b ) Why is its water usually of 
exceptional purity? 

28. Explain why the water of an artesian well rises sometimes above 
the level of the local water table. 

29. How was the “ captive sheet ” captured? 

30. (a) What is a spring? (b) A mineral spring? (c) A geyser? 

31. Name regions famous for their springs. 

32. (a) What conditions determine the volume of springs? ( b ) 
Their permanence? (c) Their location? 

33. (a) Locate several hot springs. (6) What substance is some¬ 
times deposited by them? 

34. What is a quicksand? 

35. (a) How is the water of a geyser heated? (6) Why is the 
eruption not continuous? 

36. Name three regions where geysers exist. 

37. Explain the action of a geyser. 

38. What substance is deposited about a geyser? 


REVIEW QUESTIONS 


37 


39. (a) What is formed when the water table is above the surface? 
(b) When it is at, or slightly below, the surface? (c) When it is 
too low? 

40. (a) What is irrigation? ( b) Dry-farming? (c) Describe the 
processes used in dry-farming. 


CHAPTER XX 

RIVERS 

1. Of what importance are rivers as highways? 

2. (a) How does the Mississippi illustrate the importance of river 
transportation to commerce? (6) The Great Lakes? 

3. How does the use of rivers for transportation in'Europe com¬ 
pare with their use in this country? 

4. State the advantages and the disadvantages of rivers as sources 
of water supply for cities. 

5. (a) What military advantage does a river offer in time of 
war? ( b ) Name rivers that were important during the World War; 
(c) during our Civil War. 

6. Why are rivers unsatisfactory as national boundaries? 

7. From what sources do rivers obtain water? 

8. Define river, tributary, river system, river basin, river valley, 
divide. 

9. Locate the following parts of a stream: (a) source, (6) mouth, 
(c) bed, (d) bank, (e) channel. 

10. Is the drainage of land afforded by streams an advantage or a 
disadvantage ? 

11. State facts concerning the great flood in the Mississippi Valley 
in 1927. 

12. Briefly describe three methods of controlling floods. 

13. Summarize the life work of rivers. 

14. Define corrosion, or stream erosion. 

15. Distinguish between the destructive and the constructive work 
of rivers. 

16. (a) What is a gully? (6) Explain how the formation of 
gullies on farms may be checked. 

17. Name four features due to erosion of bed. 

18. Name and define two processes by which streams loosen and 
remove particles of mantle and bedrock. 

19. In what four ways do streams transport rock waste? 



38 


REVIEW QUESTIONS 


20. (a) In which of these ways does the Mississippi transport the 
largest amount? (6) The smallest? 

21. Define comminution. 

22. Using a diagram, explain how moving water can hold particles 
heavier than water in suspension. 

23. Under what conditions does a stream form a canyon? 

24. By what action is a canyon transformed into a V-shaped 
valley ? 

25. Explain how erosion of bed sometimes makes rivers longer. 

26. Using a diagram, explain stream piracy. 

27. Name three features due to differential erosion. 

28. How are river valleys widened? 

29. Explain the meandering of rivers as they grow older. 

30. (a) Describe an undercut bank. (6) How is a cut-off formed? 

31. Name four features due to erosion of bank. 

32. Upon what conditions does the rate of erosion by a river 
depend ? 

33. (a) What are rapids? (b) How are rapids formed? 

34. (a) What are falls? (b) Describe at least two ways in which 
waterfalls are formed. 

35. Name the cities along the fall line in southeastern United 
States. 

36. (a) Show by diagram how certain falls retreat upstream, (b) 
Where will a fall disappear? 

37. (a) What are water gaps? (b) How are they formed? 

38. Describe the assorting action of a stream. 

39. How are stratified deposits formed by streams? 

40. Describe* the formation of a sand bar. 

41. What is an overloaded stream? 

42. (a) Draw a cross-section of a flood plain, and describe its 
formation. (6) Why is it highest near the river? 

43. What is an alluvial fan? 

44. (a) What is a river profile? (6) Sketch a profile that is convex 
to the sky; (c) one that is concave to the sky. 

45. (a) What is the base level of erosion? (6) The profile of 
equilibrium? 

46. (a) State the characteristics of a young river, (b) Give an 
example. 

47. (a) State the characteristics of a mature river, (b) Give an 
example. 

48. (a) State the characteristics of an old river. (6) Give an 
example. 


REVIEW QUESTIONS 39 

49. In which stage of development is a river best adapted to the 
demands of commerce? 

50. In which stage of its development is the river valley most 
favorable to agriculture? 

51. (a) How are deltas formed? ( b ) What are natural levees? 

52. In what ways may the normal cycle of a river’s development 
be interrupted? 

53. State the result of each change mentioned. 

54. Name features produced by the depression of a river at its 
mouth. 

55. (a) What is a dismembered stream? ( b ) What is a drowned 
valley? (c) An estuary? 

56. How does the elevation of a river basin at its source affect the 
length of its cycle? 

57. (a) What are rejuvenated streams? (6) Entrenched mean¬ 
ders? (c) Engrafted streams? (d) Alluvial terraces? 

58. What are the chief functions of lakes? 

59. Mention several ways in which lake basins have been formed, 
illustrating each. 

60. What kinds of lake basins are made by the streams themselves? 

61. Describe the stages in the formation of an oxbow lake. 

62. (a) Name the largest lake, (6) the highest lake, (c) two that 
are below sea level, (d) the deepest lake, and (e) the one that varies 
most in size. 

63. Mention three ways in which lakes may be destroyed. 

64. How did the fresh water Lake Bonneville become Great Salt 
Lake ? 

65. State the economic ^importance of lakes. 


CHAPTER XXI 

GLACIERS 

1. (a) What is a glacier? (6) Where are glaciers found? (c) 
What determines whether or not glaciers shall occur in any region? 

2. (a) What is the snow linet (6) How is the height of the snow 
line related to latitude? (c) What is the altitude of the snow line 
at the equator? 

3. Distinguish between alpine and continental glaciers, and give 
locations of each type. 


40 


REVIEW QUESTIONS 


4. (a) What determines the position of the ice front of the glacier? 
(6) Under what conditions will the front of a valley glacier advance; 
retreatf 

5. (a) What is the explanation of the subglacial streamf ( b ) 
Why is it usually milky in color? (c) Why does the subglacial stream 
clear in passing through a lake? 

6. (a) Give the geographic distribution of glaciers, (b) Where 
in the United States and its possessions may glaciers be found? (c) 
Where is Glacier National Park? 

7. (a) Why do we find continental glaciers only in the polar 
regions? {b) Why is there no glacier at the North Pole? (c) What 
is the nature of the ice there? 

8. (a) What is neve? (b) Why does the glacier move? (c) How 
does it move, and at about what rate do the Swiss glaciers move? 
( d ) What is regelation? 

9. Compare and contrast the valley glaciers or ice rivers with 
rivers of water. 

10. Why do glaciers move faster in the center than at the sides, 
and faster at the top than at the bottom ? 

11. (a) Explain crevasses: lateral, longitudinal, transverse, (5) 

Explain glacial mills and 'potholes . (c) How are they related to 

crevasses ? 

12. (a) Describe the kinds of work glaciers do. ( b ) What 
are roches moutonnes? (c) Explain glacial strice and glacial 
grooves. 

13. (a) Explain the origin of U-shaped valleys. (6) What are 
cirques, and how are they formed? (c) Name two ways continental 
glaciers level the land. 

14. {a) Explain moraines: medial, lateral, terminal, ground, (b) 
Is the load carried by a glacier related to its velocity of motion as in 
rivers ? 

15. (a) What are glacial tables? (b) Why do they fall from their 

ice pedestal usually in a southwest direction in the northern hemi¬ 
sphere? (c) In what direction do they fall in the southern 
hemisphere? 

16. How do the materials in the moraines differ in appearance 
from those of deposits made by rivers? Why? 

17. How do deposits made by glaciers differ from those made by 
rivers ? Why ? 

18. (a) What is stratified drift f (b) Where and how was it made? 
(c) By what names is it known? 

19. (a) Explain the origin of: kames, eskers, drumlins. (b) Where 


REVIEW QUESTIONS 41 

in New York State can examples of each of these deposits be 
found ? 

20. How can we know that present Swiss glaciers were once much 
more extensive? 

21. (a) What is meant by “ the ice age in North America ” ? (6) 
Are there such conditions anywhere at the present to merit the term 
ice age? 

22. What are some of the evidences to be found that such condi¬ 
tions as suggested by the term ice age ever existed in the United 
States? 

23. (a) Where were the centers of accumulation of the ice consti¬ 
tuting the continental glacier of this glacial period? (6) How far 
south did the glacial ice sheet reach? 

24. (a) What were some of the effects of this invasion of ice from 
the north, to be observed now? (b) Why did it not reach farther 
south? (c) How does the topography of the ice invaded region 
differ from that not invaded? 

25. (a) Trace the southern limit reached by the ice sheet across 
the United States. (6) How is this limit recognizable? 

26. (a) Why is the topography of the glaciated region in the 
United States so much younger than that of the unglaciated? (6) 
What difference in the rivers of the two regions ? 

27. What is the explanation of the numerous stone walls seen in 
New England and other glaciated regions, and their absence in 
Virginia and other regions south of the terminal moraine? 

28. The glaciated section of the United States is characterized by 
numerous lakes. Explain three ways by which the glacial ice sheet 
was responsible for these lakes. 

29. Explain the series of parallel morainic ridges in Indiana and 
Ohio southwest of Toledo as shown in Figure 265. 

30. (a) How do the glacial soils north of the Ohio River differ from 
the residual soils south of that river? (6) Are glacial soils neces¬ 
sarily better or poorer than residual soils? 

31. (a) What occasioned the glacial period? (6) Why did the ice 
sheet disappear? (c) Is it possible that we may have another glacial 
period in the United States? 

32. (a) What is the drift of the glacial period? (6) What is till? 
(c) What is the origin of the loess? (d) What reason have we to 
think the loess was deposited in the nature of natural levees along 
the banks of glacial rivers? 

33. What was the origin of the Finger Lakes of New York; of the 
Great Lakes along the northern border of the United States? 


42 


REVIEW QUESTIONS 


34. (a) Explain Lakes Duluth, Chicago, and Maumee, and their 
outlets southward. (b) When were these southward outlets aban¬ 
doned ? 

35. (a) Explain glacial Lake Agassiz, (b) Where was its outlet? 
(c) Why did it disappear? ( d ) For what is its bed now used? (e) 
What were Lakes Algonquin and Iroquois? 

36. How does the Niagara gorge serve as a measure of postglacial 
time? 

37. Explain the economic relation of the drift to (a) stream flow, 
(6) building of roads and railroads, (c) agriculture, ( d ) water power, 
and (e) mining. 

38. Explain the “ hanging valleys ” of the Finger Lakes region in 
New York. 

39. Give three explanations of the cause of the glacial period. 


CHAPTER XXII 

PLAINS 

1. ( a ) Define relief. ( b ) What is the extreme relief of the earth? 

2. Name the important relief features of the land. 

3. How does the relief of a region influence the occupations of 
the inhabitants? 

4. ( a ) Define plain, (b) State the economic importance of plains. 

5. Mention four types of plains formed by deposition. 

6. Give the reason for the nearly level surface of each of the types. 

7. Name the materials that form a marine plain, and describe 
its structure. 

8. Why are artesian wells numerous on coastal plains? 

9. Describe the soil of a coastal plain. 

10. State the location and the extent of the Atlantic Coastal Plain. 

11. (a) Give proof of its marine origin. (6) Name the products 
of this plain. 

12. (a) Locate an ancient coastal plain, (b) How can an ancient 
coastal plain be recognized? 

13. Mention several evidences of change in the relative level of 
the land and the sea. 

14. (a) State the origin of lacustrine plains. (6) What is the 
nature of lacustrine deposits? 


REVIEW QUESTIONS 43 

15. State the conditions that led to the formation of the lacustrine 
plain in the valley of the Red River of the North. 

16. Describe the floor of former Lake Bonneville. (See page 495, 
and Figure 273.) 

17. Locate several other lacustrine plains. 

18. Why did Lake Bonneville disappear? (See page 455.) 

19. State the economic importance of lacustrine plains. 

20. (a) What is a playa? ( b ) A salinaf (c) Locate a salina in 
the United States, and one in South America. 

21. Describe the flood plain of the Mississippi River. Name sev¬ 
eral other rivers having important flood plains. 

22. State the advantages, disadvantages, and dangers of life on 
flood plains. 

23. How may these disadvantages be overcome? 

24. Name two flood plains of historical importance. 

25. Mention two types of glacial plains, and locate an example 
of each. 

26. How was each type formed? 

27. Describe the structure of the deposit forming each type. 

28. What are piedmont alluvial plains? 

29. (a) What are erosion plains? (b) By what other name are 
they known? 

30. How may erosion plains be distinguished from plains of 
deposition? (See page 500.) 

31. What is a monadnock? Locate one. 

32. What does Figure 278, of Jail Rock, Nebraska, show? 

33. How were the Great Plains formed? 

34. Describe the variation in the deposits of the Great Plains. 

35. Explain the origin of the following areas of nearly level land: 
( a ) The Red River Valley in Minnesota and Manitoba. (6) The 
eastern part of Virginia, North Carolina, and South Carolina, (c) 
Louisiana, (d) central California, (e) northern Siberia, (/) northern 
Egypt. 

36. Why are some plains deserts? 

37. What is the cause of the desert about the head of the Gulf of 
California? (See page 201.) 

38. Name and locate two trade wind deserts, one of which lies in 
the rain shadow of a mountain. (See page 187.) 


CHAPTER XXIII 

PLATEAUS AND MOUNTAINS 

1. {a) Defin e plateau. ( b ) Mention three ways in which plateaus 
have been formed. 

2 V (a) What is a fault? (6) Draw a diagram of a fault and 
point out the “ throw ” of the fault. 

3. (a) What is the fault line (trace) ? ( b ) The fault plane? 

4. (a) Describe a fault plateau. ( b ) Locate one. 

5. Sketch a fault plateau showing its rock structure. 

6. Compare the erosion of plateaus with that of plains. 

7. What striking features are developed by erosion of young 
plateaus ? 

8. (a) Describe a mature plateau. (6) Has it a level upland 
surface? (c) How do we know that it ever was a plateau? 

9. Locate and state the characteristics of the Appalachian Plateau. 

10. Sketch a cross-section of the Appalachian Plateau. (See 
Figure 285.) 

11. What are the industries of the Appalachian Plateau? 

12. (a) Describe an old plateau. (5) Define mesa; butte. 

13. Compare the economic importance of a high, plateau in the 
tropics with that of a similar plateau in the temperate zone. 

14. (a) By what means may certain plateaus in arid regions be 
made fertile? ( b ) What situation favors this? (See page 285.) 

15. Define mountain peak, ridge, range, chain, cordillera. 

16. Give an example of a mountain chain; of a cordillera. 

17. (a) Describe the formation of a domed mountain, using a 
diagram, (b) Give an example. 

18. (a) Draw a diagram of fault mountains. ( b ) Explain how 
they were formed and give two examples. 

19. Show by diagram the structure of simple folded mountains, and 
name several examples. 

20. What is known about the forces that formed folded mountains? 

21. Define anticline and syncline, and draw a diagram of each. 

22. (a) Show by a diagram of several synclines and anticlines how 
we know that the Appalachian Mountains were once much higher 
than they now are. (b) Reconstruct the folds. 

23. Enumerate five types of mountains, giving an example of each. 

44 


REVIEW QUESTIONS 45 

24. (a) Why are there no trees on the tops of high mountains? 
(5) Define timber line, (c) What is its altitude in the Rockies? 

25. State four facts about the mountain-building forces. 

26. (a) Sketch the structure of the Rocky Mountains. (5) How 
do we know that the Rocky Mountains are younger than the 
Appalachians ? 

27. State three facts about the erosion of mountains. 

28. Explain why mountains are eroded more rapidly than plains. 

29. (a) What is meant by the “ period of growth ” of a mountain? 
(5) The “ period of decline ”? 

30. Define cycle of erosion of a land form. 

31. How may a cycle of erosion be interrupted? 

32. TJpon what relation does the height of a mountain at any given 
time depend ? 

33. (a) State the characteristics of a young mountain. ( b ) Give 
example. 

34. (a) State the characteristics of a mature mountain. (6) Give 
example. 

35. (a) State the characteristics of an old mountain. ( b ) Give 
example. 

36. Compare the climatic effect of changing altitude on a moun¬ 
tain with the effect of changing latitude without changing level. 
(Recall the vertical temperature gradient and the horizontal tem¬ 
perature gradient.) 

37. (a) How does the location of a mountain range with re¬ 
spect to prevailing winds, cause differences in the climates of the 
windward and leeward sides of the range? (6) Give at least three 
illustrations. 

38. Why are mountains nearly always sparsely settled? 

39. Show how mountain environment has influenced history, 
especially during wars. 

40. How does the isolation of mountain regions affect the language, 
the customs, and the progress of the inhabitants. 

41. (a) Explain in detail the retarding influence on exploration 
and settlement of a long mountain range. (6) Give example. 

42. Mention several physical features of eastern United States 
that made New York City the metropolis of the country. 

43. (a) State several reasons why mining has become an important 
industry in mountain regions. (6) Give examples. 

44. State two reasons why water power is more easily obtained in 
mountain regions than on plains. (Recall the equivalent of one 
horse power.) 


46 REVIEW QUESTIONS 

45. Contrast agriculture on mountains with agriculture in valleys. 

46. What conditions in mountain regions make irrigation of 
near-by lands possible? 

47. Why is the western slope of the Sierra Nevada Range forest 
covered, whereas the eastern slope resembles the Great Basin in 
barrenness ? 

48. What are the reasons for maintaining large forest reserves? 

49. By means of a diagram, show how a syncline may become 
a hill. 


CHAPTER XXIV 

VOLCANOES AND EARTHQUAKES 

1. Define volcano, crater, cone, lava, ash, bomb. 

2. How are volcanic cones formed? 

3. Upon what does the steepness of the cones depend? 

4. State three theories as to the origin of the heat that forms lava. 

5. From what source is the energy of an explosive eruption 
derived ? 

6. Where does the water that accompanies an explosive eruption 
come from? 

7. Account for the increasing pressure noted in explosive erup¬ 
tions. 

8. (a) Describe an ordinary explosive eruption, (b) What 
damage does it do? (c) What often follows it? (d) What some¬ 
times precedes it? 

9. What conditions permit oozing eruptions? 

10. (a) Describe an oozing eruption. (6) What damage does 

it do? • 

11. (a) Describe a young volcanic cone. (6) Mention two 
examples. 

12. (a) Describe a mature cone. (6) Give an example. 

13. (a) Describe an old cone. (6) Name three kinds. 

14. (a) Describe a volcanic neck, (h) Locate one. 

15. Describe the caldera of Crater Lake; of Mauna Loa. 

16. Describe the columnar structure of certain cooled lavas. 

17. State the distribution of volcanoes. 

18. Why are they so frequently located among young mountains? 

19. Name four gaseous products of an explosive eruption. 


REVIEW QUESTIONS 47 

20. (a) What substances are erupted in a liquid state? (6) In a 
solid state? 

21. (a) What products of an eruption retain their gaseous state on 
cooling to ordinary temperatures? (6) Their liquid state? 

22. Recall descriptions of obsidian, basalt, granite, pumice, felsites. 

23. Mention four volcanic products that have economic value, 
and name a locality where each may be found. 

24. How do the eruptions of Vesuvius differ from those of 
Stromboli ? 

25. (a) What is a dormant volcano? (b) An extinct volcano? 

26. Name and locate several extinct volcanoes in the United 
States. 

27. (a) What is the character of the eruptions of .Etna? ( b) 
W 7 here is Etna? 

28. What unusual phenomenon occurred at the eruption of Mont 
Pelee. 

29. What was the character of the eruption of Mount Katmai? 
Where is Mount Katmai? 

30. For what is the recent eruption of Lassen Peak notable? 

31. (a) Give three evidences of past volcanic activity in eastern 
United States, (b) Why are there no volcanic cones there? 

32. Explain the difference between an intrusion of lava and an 
extrusion. 

33. Using a diagram, explain the difference between a lacolite, a 
sill, a dyke. 

34. How are lava plains formed? 

35. (a) Describe the Columbian lava plateau, (b) How is it 
shown that the lava flows in this region were intermittent? (c) 
Locate this flow on Figure 135. 

36. Compare Vesuvius, Italy, with Mauna Loa, Hawaii, accounting 
for differences in mode of eruption, character of ejected material, 
and form of cone. 

37. Name three kinds of material ejected from volcanoes, and 
account for their physical differences. 

38. (a) What is an earthquake? (b) How are they explained? 
(c) What kinds of destructive effects are observed? 

39. (a) Describe the Ischian earthquake, (b) What direction did 
the force seem to have? 

40. What was learned by the study of the Charleston, South 
Carolina, earthquake ? 

41. (a) What caused the San Francisco earthquake? (6) The 
Messina earthquake? 


48 REVIEW QUESTIONS 

42. Where was the most recent earthquake of which you have 
heard? 

43. Describe the distribution of earthquakes. 

44. What causes the sea waves that often follow earthquakes? 

45. How does the velocity of the earthquake wave aid us in deter¬ 
mining conditions in the interior of the earth? 


CHAPTER XXV 

SHORE LINES AND HARBORS 

1. Recall the facts about the continental shelf, pages 227-229. 

2. Define coast, shore, shore line, beach. 

3. What is meant by the seaward migration of a shore line? 

4. Mention two agents that sometimes ..transport rock waste and 
form a sandy beach. 

5. How does rock waste make a shore line more regular? 

6. What other action provides the rock waste that forms certain 
beaches ? 

7. Describe the formation of the regular shore line at Nome, 
Alaska (Figure 322); at Wellfleet, Massachusetts (Figure 323); at 
Island Beach, New Jersey (Figure 329); at Asbury Park, New Jersey 
(Figure 324). 

8. (a) Compare the depth curves in Figure 322, and state which 
curve shows the most effective smoothing action of the waves, (b) 
In what way does Figure 325 confirm your conclusion? 

9. Using a diagram explain how bay-mouth bars are formed. 

10. Describe the formation of an offshore bar. 

11. (a) What are fault-plane shores? (b) Why are they regular? 
(c) Locate three examples. 

12. (a) What made the mainland shore line of eastern United 
States irregular? (b) Name three large bays and three minor 
irregularities in it. 

13. How was the irregular coast of northwestern Spain formed? 

14. (a) Describe the Maine coast, (b) What made it irregular? 

15. What are fiords, and how were they formed? 

16. Describe a fiord shore line. 

17. Locate and describe a shore line due to mountain folds parallel 
to the shore. 

18. How was San Francisco Bay formed? 


REVIEW QUESTIONS 


49 


19. Why is the northwestern coast of North America irregular? 

20. (a) What is a fringing reef? (6) A barrier reef? (c) Give an 
example of each. 

21. (a) What is an atoll? (6) How are coral reefs formed? 

22. Name four harbors that have influenced the spread of civiliza¬ 
tion, and explain. 

23. Define haven, harbor, port of entry. 

24. State the requirements of a good harbor. 

25. (a) How is New York Harbor protected from storm waves? 
(6) From the winds? 

26. Mention other advantages of New York Harbor. 

27. What are its disadvantages? 

28. Name other important submerged valley harbors. 

29. State the disadvantages of some of them. 

30. Describe and locate a lagoon harbor. 

31. Locate an island harbor. 

32. Name five artificial harbors. 

33. What natural agents tend to destroy harbors? 

34. Name five important coast cities, and classify their harbors as 
to origin. 

35. (a) In what respect does the Golden Gate of San Francisco 
Harbor resemble the Narrows of New York Harbor? (b) How do 
they differ in structure? 

36. Under what conditions are floating docks used in harbors? 

37. Are the docks of New York Harbor parallel to or at right 
angles to the shore line? 

38. (a) State the advantages and disadvantages of docks parallel 
to the shore line; (5) of docks at right angles to the shore line. 

39. What are the requirements of a good air port? 


PICTURE STUDIES 


FOUCAULT’S PENDULUM EXPERIMENT 
Figure 6 

In the picture nearest you place S for south, and then place in 
proper position N, E, and W. Place arrows on the floor in the picture 
to show the direction of the movement of the floor under the pen¬ 
dulum. Keep in mind that in the northern hemisphere the southern 
side of a room moves east faster than the northern side. — F. L. B. 


STUDY OF THE STAR TRAILS 
Figure 8 

1. The north sky pole is about a degree and a quarter from the 
North Star. Using the trail made by the North Star, carefully 
locate the sky pole. 

2. Knowing that the earth rotates 15° an hour, make an estimate 
of the number of hours the photographic plate was exposed to 
produce these star trails. 

3. How many degrees above the horizon is the sky pole in latitude 
43° 45' where this photograph was taken? 

4. Select two or three of the longer and brighter trails at different 
distances from the sky pole, and measure the angle between lines 
drawn from each end of trail to the sky pole. Do you find the angles 
the same? What does this prove? 

5. Account for some of the trails being brighter than others.— 
F. L. B. 


THE EARTH IN ITS ORBIT 
Figure 10 

1. Use the aphelion and perihelion distances given in the figure, 
and calculate the average distance of the earth from the sun. 

50 


PICTURE STUDIES 


51 


2. Make a drawing to show the illumination of the earth at a 
position midway between the winter solstice and the vernal equinox. 

3. Try to indicate on this drawing the size of the sun and earth, 
if they should be drawn in accordance with the scale that has been 
used. — F. L. B. 


SKY PATHS OF THE SUN AS SEEN AT THE EQUATOR 
AT CERTAIN DATES 

Figure 11 

1. Judging from the position of the sun paths at the equator at all 
times of the year, during what two seasons in the north would the 
highest temperatures be most likely to occur at the equator? 

2. Give the direction of sunrise and sunset at the four dates speci¬ 
fied in the drawing. 

3. Between what dates should the sun shine into north windows of 
a house located on the equator? Into south windows? 

4. At what time of day approximately at all times of the year 
does the sun rise and set at the equator? 

5. On what dates only is the noon sun directly overhead? — F. L. B. 


SKY PATHS OF THE SUN AS SEEN AT NEW YORK 
AT CERTAIN DATES 

Figure 12 

1. Compare the length of day on June 21 with the length of day 
on December 21 as shown in the drawing. 

2. What is the direction of the midday sun from the zenith at all 
times of the year? 

3. At what date is the noon sun highest in the sky? How many 
degrees does it lack in reaching the zenith in your latitude? 

4. A house on June 21 located at 0, Figure 11, would receive in north 
windows direct sunlight for the entire day. Compare the direction 
of direct sunlight received in the windows of a house similarly placed 
in Figure 12. 

5. The noon sun at the date of the equinoxes is how many degrees 
from the zenith? Compare this with the latitude. — F. L. B. 


52 


PICTURE STUDIES 


SKY PATHS OF THE SUN AS SEEN 
AT THE ARCTIC CIRCLE 

Figure 13 

1. In what direction is sunrise and sunset on June 21? How long 
is the day on this date? 

2. At what time of day does, the sun touch the horizon? What is 
meant by the “ Land of the Midnight Sun ” ? 

3. At what date does the sun touch the horizon at midday? 
Explain. 

4. Give an approximate date when the day would be 23 hours long 
with only one hour night? 

5. Give reasons why the summer at the Arctic Circle may be 
expected to be short in duration and high in temperature. — F. L. B. 


SKY PATHS OF THE SUN AS SEEN 
AT THE NORTH POLE 

Figure 14 

1. The sun path at the time of the equinoxes coincides nearly with 
what circle? 

2. How long does it take the sun to reach its highest position in 
the sky? To return to the horizon? How long then is the period 
of continuous sunlight? 

3. At what time of the year might the sun be said to rise? To set? 

4. By noting the position of the sun continuously- for twenty-four 
hours, how could an observer prove his position to be at the north 
pole? 

5. From a vertical position of the sun paths at the equator to a 
horizontal position at the poles, the paths have been tipped through 
how many degrees? What relation does the amount of inclination 
of sun paths always bear to the latitude of the observer? — F. L. B. 


APPARENT MOTION OF THE STARS 
NEAR THE NORTH POLE 

Figure 16 

1. At latitude 40° north what is the altitude of the North Star 
when it is directly above the north celestial pole? Directly below? 


PICTURE STUDIES 53 

2. What is the altitude of the north celestial pole at the terrestrial 
equator? The north pole? 

3. In what direction are circumpolar stars moving when below the 
north sky pole? Above it? — F. L. B. 


THE SUN DIAL 
Figure 19 

1. What time of day is indicated on the sun dial? What kind of 
time is this? 

2. By consulting the Nautical Almanac for the equation of time 
for a certain date, how would you check up the reading of the sun 
dial so as to get mean solar time? — F. L. B. 


TIME BELTS OF THE UNITED STATES 
Figure 21 

1. What is the time of day in the greater part of Florida now as 
compared with the time there before the adoption of the new position 
of the boundaries of the standard time belts? 

2. Point out cities where the time of day has been advanced one 
hour. 

3. Where may places be located giving cities a choice of two 
standard time belts? 

4. What advantages has the new location of time belt boundaries 
over the former location? — F. L. B. 


TOPOGRAPHY OF THE MOON 
Figure 22 

1. Make an enlarged drawing of a ringed valley with a volcanic 
cone built up at the center. Two or three examples of this kind 
may be seen. 

2. Notice the shadows cast by the rims of the ringed valleys. 
What does the length of the shadows indicate? —F. L. B. 


54 


PICTURE STUDIES 


ECLIPSE OF THE SUN 
Figure 27 

1. What sometimes hides the surface of the sun? Is this darkening 
of the sun real or apparent? About how long does it last? 

2. About how long are the streamers of light from the sun as 
compared with its diameter? 

3. Notice the red flames in the corona. How much, according to 
your estimation, does the height of these flames extend from the 
photosphere? — F. L. B. 


SUN SPOTS 
Figure 28 

Sun spots are holes in the visible surface of the sun that are some¬ 
times several thousand miles deep. The diameter of the larger of 
the two shown in this figure probably exceeds the diameter of the 
earth. 

The picture is most interesting. It is the first to show so much 
detail of a sun spot, and leads to much speculation. 

Some observers maintain that sun spots are cyclonic storms, and in 
support of their claims point out the close resemblance of the curved 
lines above and below the two sun spots, shown in the figure, to a 
map of the course of the winds about a low-pressure area in the 
northern hemisphere of the earth. It is difficult on this theory, how¬ 
ever, to explain the lines which are noticeable between the two 
sun spots. 

Notice the raised rim around each of the black spots. Does this 
prove or disprove the cyclone theory? 

We know that sun spots affect the magnetic condition of the earth, 
and these two sun spots seem to indicate that there is something 
else magnetic about them. 

The picture of them might very easily be mistaken for a print 
showing the magnetic lines of force above the poles of a horseshoe 
magnet. 

If it could be shown that the two sun spots were really the poles of a 
magnet, it would also explain certain other features shown in the 
photograph. 


PICTURE STUDIES 


55 


CONTACT OF MANTLE ROCK AND BEDROCK 
Figure 113 

This picture represents the upper part of a small ravine. The 
bedrock is limestone. 

1. Note the line that separates the consolidated rock from the 
loose material above it. This is the line of contact between the bed¬ 
rock and the mantle rock. 

2. Describe the mantle rock, giving an estimate of the sizes of 
the largest and the smallest particles shown. 

3. Are the exposed edges of the bedrock more like those of Figure 
114 or like those of freshly broken stone? 

4. How many vertical cracks can you count in the top layer of 
limestone ? 

5. What name is given to the dark band just below the surface 
of the ground? — A. L. A. 


CHARACTERISTICS DISPLAYED BY THE AGENTS 
OF WEATHERING 

Before studying specimens or pictures of weathered rock, let us 
recall some of the distinguishing characteristics of rocks weathered 
by the different processes. 

1. Change of temperature causes thin layers of rock to break off 
leaving miniature cliffs where a portion of the layer still adheres to 
the bowlder. This is called exfoliation. 

2. Freezing and thawing. When water freezes in a crack, it en¬ 
larges the crack and tends to split the rock. When freezing occurs 
in the pores of a rock, it breaks off flakes or chips of the rock. 

3. Wind-blown sand usually undercuts rock leaving a smooth 
surface. 

4. Plant roots growing in cracks, split rocks. 

5. Chemical action corrodes rock wherever the chemical touches 
it. Rain water contains dissolved oxygen and carbon dioxide. It 
wets the exposed surface of a rock cliff and circulates through joints 
and fissures and pores of the rock and along its bedding planes, thus 
attacking the corners and edges of every block or layer and slowly 
rounding corners and edges without leaving the ridges of exfoliate 
weathering. 


56 


PICTURE STUDIES 


EXFOLIATE WEATHERING 
Figure 116 

To follow the recitations on weathering, pages 267f-270 .— This 
bowlder was one of a large number of angular blocks that were formed 
when the internal stresses broke up a great mass of granite. Our 
problem is to find out how it became a spheroidal bowlder. 

1. What physiographic process does this picture illustrate? 

2. What physiographic agents may have been active in forming 
the feature shown? 

3. W T hat conditions made the work of these agents possible? 

4. Mention any minor feature noticed on the bowlder. 

5. What evidence do you see that layers of the bowlder have 
scaled off? 

6. What processes of weathering cause scaling? 

7. How many parts of scaled-off layers can you count? 

8. Why are they about the same thickness? 

Interesting point to be discussed if there is time to spare. — One 
naturally wonders that the removal of scales of about the same thick¬ 
ness did not leave the block in its original form, but smaller. The 
reason is that the corners of an angular block exposed to sunlight or 
even to warm air would be heated on three sides at times, as shown in 
the sketch. This would heat the small mass of rock, forming the 
corner, to a higher temperature than the middle of the block could 
reach, thus causing greater expansion and quicker scaling. Figure A. 

In the same way the edge of an angular block that is not covered 
bv another block would be heated on two sides and would scale off. 
— A. L. A. 


WEATHERING GRANITE 
Figure 114 

It has been well established that, while still covered by a thick layer 
of other rocks, the granite split into angular blocks, each of which 
fitted into place like the stones in a wall. Weathering did not affect 
these stones until the overlying rocks were worn away, so that the 
granite was exposed to the air or to surface waters. 

1. Which of the blocks of rock show evidence of-exfoliate weather¬ 
ing? 


PICTURE STUDIES 57 

2. Explain why the lower side of these blocks is not weathered 
as much as their top sides. 

3. Which of the above processes is the probable cause of the 
widening of the vertical joints? Give reasons. — A. L. A. 



Effects of changes in temperature and chemical weathering on angular rocks. 


WEATHERING LAVA 
Figure 115 

The Absaroka range, named for the Crow Indians, is just east of 
the Continental Divide in Wyoming. The lava shown is a part of a 
great lava flow that covered many hundreds of square miles of north¬ 
western United States. In its original form the lava probably had a 
smooth upper surface, and the peculiar forms that terrified the 
Indians are the result of weathering. 

In the deep valleys between these pinnacles, particles of lava 
loosened by weathering begin their journey to the Gulf of Mexico. 
Some of them have paused for a while at the foot of the cliff, form¬ 
ing a steep pile of rock waste known as a talus slope. (See page 283.) 

Because of its elevation (12,000 feet) these mountains have abun- 









58 PICTURE STUDIES 

dant precipitation and supply water to two important tributaries of 
the Yellowstone River. 

1. Compare the weathered lava with the weathered granites of 
Figures 114 and 116. 

2. Examine the figure for blocks of lava that have fallen from the 
cliff, and for places from which other blocks have been removed. 

3. Note the deep but narrow valleys cut in the upper portion of 
the lava. Ho\^ many of them can you find? 

4. Account for the rills (little water courses) on the talus slope, 
that lead from points directly below each of the deep valleys to a 
larger water course, the group resembling a trunk stream and its 
tributaries. 

5. What substance is present in rain water that makes it active in 
weathering igneous rock? 

6. What name is given this process of weathering? 

7. When it rains, the sides and the bottom of the little valleys at 
the top of the lava are equally wet. Why, then, should not the 
valleys have been widened as rapidly as they were deepened? 

Point of interest. The lava in this figure, like most lava, is without 
joints. Why was it not broken like the granite of Figure 114? 
— A. L. A. 


WEATHERING ABOVE THE TIMBER LINE 
Figure 117 

The building here shown is a station of the United States Weather 
Bureau, on the top of Pike’s Peak, 8000 feet above the plains at the 
base of the mountain. 

The broken rock on top of the mountain is not covered with soil, 
because rock waste is carried away by rain, melted snow, and winds 
about as fast as it is formed. At lower levels there are talus slopes. 

1. Are the rocks of this picture angular or spheroidal? 

2. Which agents of weathering produce rounded forms? 

3. Which angular? 

4. Of those mentioned, which probably broke up this rock ? Pike’s 
Peak is just the right height to permit daily freezing and thawing at 
certain times of the year. 

Whenever the daily average temperature is 60°F. at its base, the 
day and night temperatures will be 33° and 27° respectively. 

Recall the vertical temperature gradient and compute the average 


PICTURE STUDIES 


59 


daily temperature 8000 feet above a plain when the average tem¬ 
perature at the base is 60°F. At an elevation of 8000 feet the day 
and night temperatures would differ by about 6°. 


WEATHERING ROCKS OF UNEQUAL RESISTANCE 
Figure 119 

The rounded masses on top of pedestals are called concretions. 
They are formed of materials deposited by water that circulates 
through crevices or the pores of bedrock, page 377. 

Concretions differ from the surrounding rock in composition and 
resistance to the action of the agents of weatherings. 

1. Point out the concretions. 

2. Which rock is least resistant to weathering; that of the concre¬ 
tions, that of the layer containing the concretions, or the layer near 
the ground? 

3. Which of the three is most resistant? 

4. Which of the agents of weathering produce an uneven surface 
and which a smooth surface? 

5. Which of the above agents could not have formed the pedestals 
that support the concretions. 

Another illustration of unequal weathering is seen in Figure 118. 
Certain of the layers stand out in relief because more resistant. 
Account for the holes in the side of the middle outlier. — A. L. A. 


STUDY OF A GULLY IN MANTLE ROCK 
Figure 202 

To 'precede the first lesson on stream erosion. — All books open to 
Figure 202. 

In the foreground of this picture, you will see just beyond the fence 
a small stream that curves around a valley flat on the farther side of 
the stream. Beyond this flat land is a steep slope that rises ten or 
twelve feet to a second gently sloping field. We thus have a steep 
slope between two gentle slopes. 

One day, after a heavy shower, the owner of the upper field found 
that a portion of his land had been washed away. 

1. Place your pencil points on the land that was washed out. 


PICTURE STUDIES 


60 

2. Locate the place from which the materials came. The notch 
from which the soil was removed is called a gully. 

3. On which of the three slopes should you expect the soil to be 
carried away most rapidly at first? Give your reason. 

4. Why did the running water remove the soil from one place and 
deposit it at another? 

5. What effect do such gullies have upon the value of the field? 
Why? 

6. Is there any way of preventing further deepening of the gully? 
(See page 403.) 

7. Compare Figures 202, 239, and 240, each of which shows an 
alluvial cone, and determine which of them has a fan-shaped base. 

8. If a cone is a pyramid with a circular base, which of the three 
figures shows the best cone? 

9. Are they cones or half-cones? 

These cones or half-cones were formed by running water that 
eroded the soil, transported it a short distance, and deposited it, 
thus illustrating the work of all streams. 

Running water is not the only agent that forms conical piles of 
mantle rock; in fact, this is the natural form assumed by all loose 
materials dropped in a given place, whether it be grain issuing from 
an elevator spout, a carload of coal dropped through a trestle, or the 
material of a landslide at the foot of a mountain. — A. L. A. 


AUSABLE CHASM, NEW YORK 
Figure 206 

The rock walls of Ausable Chasm are Potsdam sandstone, one of 
the most durable rocks known. In some exposures the sand grains 
forming this rock are so firmly cemented together that the rock has 
very little porosity, and is sometimes called a quartzite. 

1. What processes were concerned in forming the chasm? 

2. What physiographic agent or agents have been active in the 
past? 

3. What agents are now active? 

4. State the relation between the constructive and the destructive 
processes that have affected the region illustrated. 

5. What human interests have been affected by the changes sug¬ 
gested by this picture ? 

Figure B shows the relative levels of the chasm, Lake Champlain, 


PICTURE STUDIES 


61 


and the Atlantic Ocean. The horizontal distances between the points 
mentioned are not indicated in the sketch. C is the shore of the lake, 
and the line CD is the level of the lake. The zero line is the level of 
the ocean. 

6. Has the river accomplished its work through abrasion of solu¬ 
tion of the bedrock? Recall the solubility of sandstone. 

7. How does the present velocity of the river compare with its 
velocity when it began to erode the chasm? 

8. To what level can the river erode its valley? 

The level at which erosion ceases is called base level. (See page 
499.) The level of Lake Champlain is a local base level for the 
region that is drained into the lake and limits the erosion of all rivers 
that flow into it. 

Sea level is a continental base level and limits the erosion of all 
rivers that flow into the sea, thus preventing further lowering of the 
continents by this process. 

9. What area in the figure represents the total work that Ausable 
River can do? 

10. What characteristics give Ausable River its great eroding 
power ? 



Section of Ausable Chasm. 


WEATHERING CANYON WALLS 
Figure 226 

1. Is this a single fall or a series of falls? 

2. Can you find four falls? 

3. Is this a swift or a sluggish' stream? How do you know? 









g2 PICTURE STUDIES 

4. What does,the rounded form of these bowlders indicate? 

5. If the stream had ability to transport them to this point, why 
did it drop them here? 

6. Are they likely to remain here permanently? Why? 

7. How did they assist in eroding the bed of the stream? 

8. Where did the soil on the slopes come from? 

9. Can you see any evidences of weathering, such as talus slopes, 
fragments of rock on ledges, etc.? 

10. Is this a canyon or a V-shaped valley ? 

Figure C. Diagram of work of erosion of bed and of weathering. 

In the diagram let the lines 5, 2, 3, 6 represent the space excavated 
by erosion of bed and the triangles 1, 2, 5 and 3, 4, 6, the portion 
removed by the agents of weathering. 

11. If the width of the stream 2, 3 is equal to the lines 1, 5 and 
6, 4, how would the work done by erosion of bed compare with that 
done by weathering? — A. L. A. 



ANCIENT LAKE BONNEVILLE 
Figure 273 

The region about Great Salt Lake is often called the Great Ameri¬ 
can Desert, but it has not always been arid. Examination of the 
deposits that form the level surface shown in the picture reveals the 
fact that they accumulated on the floor of a lake. The shore line of 
this lake is found high up on the slopes of the mountains that sur¬ 
round the basin, and has been traced hundreds of miles by the 





PICTURE STUDIES 


63 


beaches, sandbars, and deltas formed when the basin was filled with 
water, indicating that a lake nearly as large as Lake Superior and 
1000 feet deep once covered this arid region. 

1. What three physiographic features are shown in Figure 273? 

2. What is the rainfall in the Great Basin? (See pages 201 and 
213.) 

3. Recall the history of Great Salt Lake. (See page 201.) 

4. State the cause of the present arid condition in this region. 
(See page 449.) 

5. What climate would you expect if there were no mountains on 
the west of the basin? 

6. During the glacial period (page 474) the climate in this region 
was colder and the precipitation greater than at present. The sur¬ 
rounding mountains were snow capped, and great glaciers were 
formed, some of which extended from the top of the Wasatch Moun¬ 
tains to the shores of Lake Bonneville. Briefly state the conditions 
that made Lake Bonneville possible. 

Point of interest. — The water of Great Salt Lake contains so much 
salt that a bather does not sink. Thousands of barrels of salt ex¬ 
tracted from the water are sold yearly. 

7. The deposits formed in the lake contain two layers of rock salt 
separated by layers of lacustrine deposits. What changes of climate 
does this indicate? 


STANDARD TIME BELTS AND THE 
INTERNATIONAL DATE LINE 

The process of computing the standard time of different time belts 
at the same instant is simpler than that of computing the mean solar 
time of different cities, and results in just as clear ideas of the relation 
between longitude and time. For the purposes of this exercise we 
have, therefore, assumed that the Standard Time System, adopted 
by the United States in 1883, has been extended to all parts of the 
world. 

The fact that the earth rotates through 360° in 24 hours, or 15° an 
hour, and one degree in four minutes, enables us to compute the 
difference in the times of any two places when we know the difference 
in their longitudes, or to compute the difference in their longitudes 
when we know the difference in their times. 

Nearly all good globes have meridians drawn 15° apart, and the 
mean solar times of these meridians therefore differ by exactly one 


64 


PICTURE STUDIES 


hour. These 24 meridians are taken as the central meridians of the 
time belts, each of which extends 7^° each side of its meridian. 

Since the earth rotates toward the east, these meridians pass under 
the vertical rays of the sun at intervals of one hour each meridian, 
having its noon one hour later than the meridian next east of it, and 
one hour earlier than the meridian next west of it. 

If such a globe as that mentioned is available, the determination 
of the difference in time between any two places is simply a matter 
of counting the number of meridians between them, allowing one 
hour for each belt. 

In the absence of such a globe, the diagram below may be used in 
the same way. It represents the earth as seen from directly above 
the north pole. 

The large circle is the equator, which is divided into 24 parts, each 
being 15° wide and representing about 1000 miles at the equator. 


LlI 







PICTURE STUDIES 65 

The dotted lines are the central meridians of the time belts, and 
the full lines are the boundaries of the different time belts. 

Arrows indicate the direction of rotation of the earth. — A. L. A. 

We can determine differences in time or in longitude with this 
diagram just as we can with the globe. 

Suppose we wish to find the standard time at Naples, 15° east 
longitude when it is noon in Chicago, 90° west longitude. We place 
our pencil on the meridian 90° west and say 12 noon; on the next 
meridian east, 1 o’clock p.m.; then 2 p.m.; and so on to 7 p.m. at 
Naples the answer. 

Problems 

1. What is the standard time at 105° west longitude when it is noon 
in London? 

2. What is the standard time in Calcutta, 90° east longitude, when 
it is noon in London ? 

3. What is the standard time in Sidney, Australia, 150° east longi¬ 
tude, when it is noon in London? 

4. What is the standard time at 135 east longitude when it is 9 p.m. 
in London? 

5. What is the standard time at Nome, Alaska, when it is noon in 
New York City? 

6. What is the standard time in Iceland when it is noon in the 
Canary Islands, 15° west longitude. 

7. What is the longitude of the meridian on which it is 3 a.m. the 
same day when it is 8 a.m. in New York? 

8. In what longitude is it 3 a.m. the next day when it is 12 o’clock 
noon in New York? 

9. When it is 5 o’clock a.m. in New York, what is the longitude of 
a place having 1 o’clock a.m. the same day? What that of a place 
having 11 p.m. the previous day? 

10. When it is noon by the ship’s local time and the ship’s chro¬ 
nometer carrying London time shows 9 o’clock p.m., what is the longi¬ 
tude of the ship ? 

11. What is the standard time at Kyoto, Japan, 135° east longitude 
when it is 8 o’clock p.m. in Denver, Colorado? (Count toward the 
east, and state the hour and day.) 

12. Solve the eleventh problem counting toward the west, and 
state the hour and day. Why do you not get the same answer? 

By common consent it is agreed that a given date shall appear 
upon the earth for the first time when the 180th meridian reaches 
its midnight position. This meridian is called the date line. 


66 


PICTURE STUDIES 


If we let the diagram, Figure D, represent the 180th meridian in its 
midnight position and call the new day that is just beginning March 
1, 1928, we shall see that the next meridian to come to the midnight 
position is the 165th, east longitude, which begins its March 1 an 
hour later than, the 180th meridian, and that the meridian of London 
will begin this date twelve hours after the 180th did so. How long 
after the 180th meridian began its March 1 will the 165th meridian, 
west longitude, begin its March 1? 

Is it true that the times of these two adjoining time belts differ by 
23 hours ? 

If you cross the date line in a direction opposite to that of the 
rotation of the earth while counting time belts, you will find it nec¬ 
essary to add 24 hours to the time just as ships do when they cross it 
in the same direction. 

If you count across the date line in the same direction as the rota¬ 
tion of the earth, you will have to subtract 24 hours from the time. 

Remember these two points, and you will get the same answer 
whichever way you count. 


TO DETERMINE THE LATITUDE OF A PLACE 

In ancient times latitude was quite accurately determined from 
observations of the gnomon mentioned on page 7. The method used 
was to compute the angle on June 21 between the sun’s rays, and a 
vertical line, by measuring the length of the shortest shadow of the 
year. The ancients knew that the angle between the sun’s ray and 
the gnomon, Figure 2, was equal to the angle at C, which is the same 
as saying that measuring the length of the shadow will tell you the 
angle at the center of the earth between the sun’s vertical ray and 
the line from the observer to his zenith. 

Six months later, when the sun cast its longest shadow, they com¬ 
puted the angle again, and the average of these angles gave them the 
latitude of the place. 

With a sextant, page 28, when all corrections are made, the position 
of a ship may be determined within half a mile. With the great 
transits of our observatories latitude is determined with very much 
greater accuracy. 

For our purpose the principle used by the ancient astronomers is 
chosen, because it eliminates two of the larger corrections, because 
the apparatus is simpler, and because it measures the zenith distance 
of the sun directly, not its noon altitude 


PICTURE STUDIES 


67 


A miniature gnomon can be made of a half-inch brass rod about 
14 inches long fastened to a circular base at the exact center of the 
circle. The brass rod should have a sharp point at the upper end. 

When ready to perform the experiment, place a table in a south 
window or out of doors,' adjusting it so that the top is perfectly level. 



A, plumb bob: B, mirror: C, screw for levelling base. Arey apparatus. 


Then place a large sheet of paper on the table, fastening it with 
thumb tacks. 

Place the gnomon near the center of the window side of the paper, 
and draw a pencil line around the base of the gnomon as close to the 
base as possible. 

Beginning about 15 minutes before solar noon, mark the exact 
position of the shadow of the point of the gnomon; repeat this every 
two minutes until about 15 minutes past solar noon. 










































68 


PICTURE STUDIES 


Draw a smooth curve through the points located, and determine 
what point in the curve marks the shortest shadow. Measure the 
distance from this point to the circle drawn about the base of the 
gnomon, and add to it one-half the diameter of the circle. This sum 
is the length of the shortest shadow for the given date. 

Now measure the exact height of the gnomon, and construct the 
triangle formed by the sun’s ray, the gnomon, and the shadow. 

On the triangle measure the angle at the point of the gnomon with 
a protractor reading to at least 15'. This is the zenith distance of 
the sun at solar noon. 

Now note whether the shadow of the gnomon was on the south or 
the north side of the gnomon. This will tell you whether the sun is 
south or north of you. 

Consult the Nautical Almanac (or other almanac) for the sun’s 
declination at the time of the observation, and compute the latitude 
of the place by the following rule: 

If the sun is between the observer and the equator, his latitude is 
the sum of the zenith distance and the sun’s declination; in all other 
conditions his latitude is the difference between these two quantities. 

The Arey apparatus shown in the figure is easily constructed. It 
has the following advantages: It measures the zenith distance directly. 
The line casting the shadow is always horizontal. A set screw pro¬ 
vides for the adjustment of the plumb line to the zero of the scale. 
It is not necessary that the surface on which the apparatus rests be 
absolutely horizontal. 
















1 


I 




































f ^ 


LIBRARY OF CONGRESS 



0 027 133 124 1 


Photographs of Physiographic Features 

Photographs sixteen by twenty inches for classroom use may be obtained 
from the authors. The first set of ten is now ready. Other sets will be 
issued from time to time. A circular describing these sets may be obtained 
from the address below. 

1. The River’s Tools (a study of erosion, Queechee “Gulf,” Vermont) 

2. Recession of Falls ( Yellowstone Canyon) 

3. Lateral Erosion and Terraces ( Upper Snake River, Wyoming) 

4. Flood Plain and Meanders ( Valley of the Milk River) 

5. Mer de Glace (an Alpine glacier) 

6. Glaciers of the Himalaya mountains ( A . Snow Field of the Tarim 

Sehr glacier; B. Great Saichen glacier) 

7. Parellel Joints ( three sets) 

8. Uplifted Sedimentary Rocks ( Mount Robinson) 

9. Telephoto of the “Top of the World” ( Mount Everest) 

10. Surf near Tillamook Head, Oregon 

Suggestions as to the points that may be brought out by class discussion 
accompany each picture. Price $15 per set. Single pictures $2.00 each, 
postpaid. 

Arey and Bryant, 

Roslyn Heights, New York 






